






























































































































































































































































































































































































































































































































































































































































































































































































































































































































A 


PRACTICAL COURSE 


MILITARY SURVEYING, 

INCLUDING 


THE PRINCIPLES OF TOPOGRAPHICAL DRAWING. 







'*> 6 


BY 


CAPTAIN LENDY, P.G.S., F.L.S., &c., 

A 

DIBECTOB OF THE PBACTIOAL MILITARY COLLEGE AT SUNBURY. 


LONDON: 

ATCHLEY AND CO., 

pMii^rs ai mb guptttutnl 

L06, GREAT RUSSELL STREET, BEDFORD SQUARE, W.C. 

1864. 

[The right of Translation is reserved .] 







U.Q 

U 5 t 


LONDON : 

SAVILL AND EDWARDS, PRINTERS, CHANDOS STREET, 
COVENT GARDEN. 









* 

% 

f • 

v J 

> 


PREFACE. 


Topography is to Military Science wliat Music is to feminine 
accomplishments : it does not claim the first rank, but an accom¬ 
plished officer should he familiar with it. 

The subject is in itself of the greatest simplicity, the only founda¬ 
tion requisite for a beginner being a trifling amount of Greometry: 
yet very few officers, Sandhurst and Woolwich men excepted, can 
make a survey—nay, read a plan. 

This, I believe, is to he accounted for by the want of fixed rules 
to figure the ground. At his first step a beginner is lost among the 
endless varieties of horizontal style, vertical style, pencil-brush work, 
&c., the mutual relations of which he is unable to understand; and 
furthermore, bewildered by the cobweb of the plotting hook, and the 
screws of the theodolite, he readily gives up the attempt. 

In the following pages, originally written for the Military College 
of Sunbury, I have endeavoured to remove the difficulty in explaining 
the theory of the ground, and confinifig^ myself to those practical 
operations only which are needed in actual service. 

Major Petley, the head professor of Military Surveying at the Eoyal 
Military College, has kindly favoured me with his excellent series of 
plates (xi to xvii) illustrating the horizontal method, and Captain 
Eicliards, the talented instructor in Military Drawing, at the same 
Institution, has obliged me with a Military Sketch on the same 
system, (xviii.) 



IV 


PREFACE. 


The vertical system I have, I trust, rendered equally intelligible by 
a series of plates, properly graduated. 

Lastly, for the operations of the field, I have carefully avoided the 
intricacies of trigonometrical surveys, and exclusively employed the 
most simple instruments. 

I thus venture the publication of this volume, feeling confident 
that an officer who will steadily repeat on the ground the operations 
therein described, will soon become competent to make a good Military 
Sketch. 


Sunbury, June, 1864. 


A. F. LENDY. 


CONTENTS. 


CHAPTER I. 

DEFINITIONS. 

Topography—Military Surveying—Models—Plans—Military Sketch—Reconnaissance— 
Geodesy—Geography—Planimetry—Levelling—Scales—Scales employed in Mili¬ 
tary Surveys .pp. 1 — 6 


CHAPTER II. 

TOPOGRAPHICAL DRAWING. 

§ I. Conventional Signs of Planimetry. 

Objects to be represented in a Military Plan—Conditions which such a Plan should 
fulfil—Table of the Signs adopted in the Ordnance Survey—Minute—The Light 
supposed Vertical—Colouring—Hints on the Drawing of the Signs . pp. 7—9 

§ II. Representation of the Ground. 

Conditions to be obtained— Geometrical Method —Horizontal Contours—Burr’s Experi¬ 
ment—Equidistance of Contours—Profiles and Elevations can be made—This 
Method is generally accepted—Shading of the Ground—Vertical Light—Difficul¬ 
ties met with. English Systems —Horizontal Style the best for Military Sketches— 
Vertical Style. French System combines expression with accuracy—Directions to 
draw the Hachures—Diapasons. German System— -Lehman’s method. Brushing — 
Oblique Light — Perspective ........ pp. 10—18 

§ III. Features of the Ground. 

Watershed—Basin—Crest—Table Land— Col —Defile —Hills—Counterforts —Valleys 
—Vales—Ravines—Remarks on Drawing Hachures . . . pp. 19—23 

§ IV. Copy and Reduction of Plans. 

Copying at the same Scale—Order in which the Objects are Drawn—Reduction to a 
different Scale—How to proceed when the Area is to be reduced in a given 
proportion ........... pp. 23—25 


CHAPTER III. 

TRIANGULATION. 

Triangulation—Filling-in of the Details—Military Method—Base Line—Form of the 
Triangles—Length of the Base and Dimensions of Triangles—Two Methods to 
make the Canvas, Calculation or Construction—The latter exclusively employed for 
Military Surveys—Plotting in the Field ..... pp. 26—29 




VI 


CONTENTS. 


CHAPTER IV. 

DISTANCES. 

Chaining —Pacing—Riding—Rough Valuation of Distances. Construction of Scales — 
Scales of 6 in. and 2 in. to the mile—Scale of —Scale of Paces—Scales for 

Riding—Scale for a foreign plan—Reduction of Distances to their horizontal Pro¬ 
jection—How to Trace or Signal a Direction . . . . pp. 30—36 

To what account Chaining or Pacing can be turned—To Trace on the Ground a 
Perpendicular to the Extremity of a Line which cannot be produced—To find the 
Distance between Two Points, one of which is inaccessible—To make an Angle 
equal to a given Angle—Through a given Point to draw a Line parallel to a 
given Line—How to produce a Direction beyond an Obstacle—How to find the 
Distance between two inaccessible Points—To bisect an- Angle—To find the 
Direction of the Capital of a Work—To find the Height of a Building—To fix 
on a Plan the Projection of a Point, having on that Plan the Projections of Two 
Lines; or having the Projection of a Line on which the Point stands, and the 
Projection of an accessible Point—The Projections of two Points being given, to 
fix on the Plan the Projection of a Third, which is inaccessible—To find the 
Projections of several Points ........ pp. 37—48 


CHAPTER V. 

PRISMATIC COMPASS. 

% 

Magnetic Azimuth—Bearing—Prismatic Compass ; its use—Protractor; its use—To 
find the Projection of a Point, knowing those of two others—Method of Intersec¬ 
tion—To find one’s place in a Survey—To Survey a Road—Method of Traversing 
—Taking the back Angle—To trace the Direction of the Capital of a Work— 
Echelle rapporteur Trinquier ........ pp. 48_ 95 


CHAPTER VI. 

PLANE TABLE. 

Various descriptions of Plane Tables—Use of the Plane Table—To fix the Projection of 
a Point having those of two Accessible Points—Ditto, When one of the two Points 
is inaccessible; Ditto, When the two Points are inaccessible—To fix the Projection 
of two accessible Points, being given those of two inaccessible ones—The Projec¬ 
tions of three inaccessible Points being given, to find the projection of an accessible 
Point—To find one’s Place in a Survey—Addition of a Compass to the Plane 
Table—Plane Table of Major Fevre ; his Scale .... pp. 59_ 6g 


CONTENTS. 


Vll 


CHAPTER VII. 

SEXTANT AND CROSS-STAFF. 

Box-sextant; its adjustment; its use—Vernier—Box-sextant less advantageous than 
the Prismatic Compass—Principle of the Box-sextant—Problems it enables to 
solve ..pp. 69—75 

Cross-staff; its various forms—Through a given Point to trace a Perpendicular to a 
given Line—To produce a Direction beyond an Obstacle—Through a given Point 
to draw a Line parallel to a given Line—To find the Distance between two Points, 
one of which is inaccessible—Ditto, both Points are inaccessible—To Survey a 
Polygon or a River—To find the area of a Field .... pp. 75—79 


CHAPTER VIII. 

LEVELLING. 

Levelling—Clinometer and Box-sextant give the Angle of Elevation—The Difference of 
Level is then calculated—Tables—French Water-level; its use to measure directly 
the Difference of Altitude—A Substitute for it—Levelling with a Chain—Level¬ 
ling with the Plane Table—Clinometer Trinquier ; its description—This instrument 
gives the Angle of Elevation, the Horizontal and the Vertical Distance between 
two Points ........... pp. 80—90 


CHAPTER IX. 

MILITARY SURVEYING. 

Preliminary Operation—Selection of Triangles—Measure of a Base—Triangulation— 
Tracing the Meridian Line—Subdivision of Labour—Filling in the Details— 
Traverse and Intersection—Details—Representation of the Ground—Canvas of 
Levelling—Preliminary Sketches—Tracing the Contours with a Water-level— 
Ditto, by means of the Altitudes of the Chief Points—Ditto, by means of the 
Angles of Depression or Elevation—Memoire. .... pp. 91—102 


CHAPTER X. 

MILITARY SKETCHING. 

A Survey best Introduction to Sketching—Sketching—Hints as to Details—Surveying 
at Sight—Instruments made in the Field—Itineraries—Sketching from Memory—- 
Sketching from Description—Reconnoitring—Report—Table to Guide in the 
Redaction of a Memoire ........ pp. 103—122 




LIST OP THE PLATES 


1. Conventional Signs. 

2. Ditto. 

3. Ditto. 

4. Ditto. 

5. Chief features of the ground represented by Contours. 

6. Sections of ditto. 

7. Elementary Plan. 

8. The ground figured by Interpolated Contours. 

9. Another Horizontal Style. 

10. The ground of Plate V. figured in the above style. * 

11. The Horizontal Style taught at the Royal Military College (Major Petley’s). 


12. 

Ditto. 


Ditto. 

13. 

Ditto. 


Ditto. 

14. 

Ditto. 


Ditto. 

15. 

Ditto. 


Ditto. 

16. 

Ditto. 


Ditto. 

16 a. 

Ditto. 


Ditto. 

17. 

A Military Sketch from Major 

Petley. 

18. 

Ditto by Captain 

Richards. 


19. 

Ditto in a different style. 


20. 

Ground figured in 

the Yertical Style. 

21. 

Ditto. 

Ditto. 


22. 

Ditto. 

Ditto. 



23; Ground of Plate Y. in the Yertical Style. 

24. Military Sketch in the Yertical Style. 

25. Ground figured by shading with Indian ink (light vertical). 

26. The same, with oblique light. 

27. Ground figured in Perspective. 

27 a. Eye Sketch. 

28. First stage of a Copied PlaD. 

29. Second ditto. 

30. Third ditto. 

31. The same completed. 

32. Reductions of the same. 

33. Specimen of Engraved Plan. 

34. Photo-litho of the English Ordnance Survey (scale 1 inch to the mile). 

35. Photo-litho of the French Ordnance Survey (scale -gtnrtro) - * 

36. Sketch of a Road in Yertical Style. 

37. Ditto in Horizontal Style. 

38. Sketch given to the Candidates for admission to the Staff College in 1861. 

39. Ditto in 1863. 

40. A Military Sketch by Major Petley. 


* It is next to impossible to compare the English and French maps ; the English diapason gives a 
much darker shading, and its scale is different. In order to compare them properly, the same ground 
should be represented on the same scale. 





A PRACTICAL COURSE 


OF 

MILITARY SURVEYING. 


CHAPTER I. 

DEFINITIONS. 

(1.) Topography (surveying) is the art of describing a limited part of 
the surface of the earth, so as to give a good idea of its configuration 
and the resources it presents. 

The purpose of military topography (military surveying) is to describe 
clearly the ground and position of all objects scattered over its surface 
that have any military importance. These objects are either natural, 
as mountains, hills, valleys, rivers, marshes, &c.; or artificial, as houses, 
enclosures, walls, fortifications, &c. All are of some military importance, 
since they can modify the action of troops. 

The description of the surface of the earth was originally made in 
writing, by a greater or less number of notes: these were rather difficult 
to use. Imitative drawings came into use much later. 

(2.) The ground can be represented in two manners : by models or 
by plans. 

Models are made of plaster or wood, and, like a sculpture, present in 
a small compass the exact image of the elevations and depressions of 
the ground. They are expensive, take much time, and their size and 
weight render them unavailable for field purposes. Their sole 
advantage is to represent the ground to persons not familiar with the 
reading of maps. Of such use are the models of Sebastopol, Waterloo, &c., 
at the United Service Institution. 

B 



2 


A PRACTICAL COURSE OF MILITARY SURVEYING. 


K plan or map is a figure which by means of a few conventional 
signs represents all the natural and artificial objects above alluded to 
in their relative position. Unlike relievos, a plan can be taken into 
the field, and is indeed an indispensable item in war. 

By means of plans the general prepares all his operations, battles, 
sieges, marches, encampments, entrenchments, &c.; by their help the 
great deeds of war are put down in records which afiord to history the 
most valuable materials, and to the art of war the most useful lessons. 

(3.) Topography is an indispensable complement to all the military 
sciences, fortification, tactics, &c., since the application of their 
principles entirely depends on the nature of the ground; and as it is 
most important for an officer to appreciate at a glance the distances, 
slopes, and in general all the mutual relations of the various parts of a 
field of battle, he should remember that this coup d’ceil militaire is only 
acquired by the practical study of Topography. 

(4.) When a plan is intended to serve as a guide to prepare con¬ 
structions on the ground, such as fortifications, buildings, &c., it is 
made with accuracy, and the survey is called regular. When, however, 
a less accurate description is needed, a survey more or less rapid is made 
according to the purpose in view; the survey is then called irregular , or 
reconnoitring , and the plan is named a military slcetch. 

In regular topography the execution of the plans requires precise 
methods, good instruments, and time; but in irregular surveys and 
reconnoitrings, instruments of a less accurate description are sufficient: 
sometimes they may be dispensed with; thus military sketches are 
made at sight, from memory, and even from mere indications and 
reports. 

Military surveying is very seldom regular, because while time is 
always precious in the field, instruments are not always to be had, and, 
above all, because a great accuracy is not needed. The plans of fortifi¬ 
cation, those of attacks in a siege, demand, however, some precision. 
Regular surveying should be studied first, because it is through a 
thorough acquaintance with its principles and methods, together with 
a fair amount of practice only, that an officer will be able to make a 
military sketch expeditiously and without instruments. 

(5.) Topography describes limited parts of the surface of the earth 


DEFINITIONS. 


3 


only: when those parts exceed sixty miles in length, more accurate 
methods are resorted to, and form the province of geodesy. This science 
enables us to describe considerable tracts of land, such as kingdoms, 
&c.; it furnishes the materials for geography , and gives to topography 
the exact position of the important landmarks. By means of calcula¬ 
tions and practical operations it determines with great precision the 
relative position of the chief points of a country, such as summits of 
mountains, intersections of valleys, steeples of churches, &c., leaving 
aside all details. Topography, on the contrary, represents all the 
details lying between two or three of these points, and its operations 
are exclusively practical. 

(6.) The plan of a certain extent of ground is a figure similar to the 
projection of all the points of that surface on a horizontal plane; a 
projection being the foot of the perpendicular drawn from a point to 
the plane. In topography this plan is tangent to the surface of the 
earth, and the earth being spherical, the spherical segment abc cannot 


Fig. 1. 



be represented exactly on the circle a b c. As, however, the error does 
not exceed three yards in sixty miles, it matters but little if we consider 
the earth to be plane in topography. When, however, the surface to be 
described is large, the sphericity cannot any longer be neglected, and 
geodesy takes it into account in the survey of a country. 

(7.) Since topography describes both the objects lying on the 
surface of the earth and the undulations of that surface, it may be 
divided into two parts : planimetry , or the making the plan of those 
objects; and levelling , or representing the ground itself. Should the 

b 2 








4 


A PRACTICAL COURSE OF MILITARY SURVEYING. 


ground be exactly level, topography would consist of planimetry 
only. 

In order to represent on paper the various details of the surface of 
the earth, a few conventional signs have been adopted, and the student 
should, first of all, render himself thoroughly familiar with their 
meaning, and acquire some practice in drawing them. When he 
knows them so as to read or copy a plan, he has mastered one of the 
essential parts of topography. Before passing those signs in review 
we must say a word or two about the scale of the plan. 

(8.) The representation of a given surface of ground can be made 
of different sizes according to the end in view, it being clear that the 
greater the accuracy required the larger the drawing must be. 

The size of a dimension of the plan compared to that of the ground 
which it represents is called the scale of the plan. Thus, if a road one 
mile in length occupies but one inch in the drawing, the scale is that 
of an inch to the mile. If a wall 600 yards long is represented by a 
line one inch long, the scale is that of an inch to 600 yards. 

Sometimes this expression is reversed, and we say, the scale of 12 
chains to the inch, of 4 miles to the inch, &c.; it signifies that an inch 
of the plan represents 12 chains, 4 miles, &c., on the ground. 

It may also happen that the scale be indicated by a representative 
fraction, such as mrro or to-utto, &c. ; it implies that the dimensions 
of the plan are 2000, 40,000, &c., times smaller than the corresponding 
ones on the field. 

We may readily pass from one form to the other; for instance, the 
scale of one inch to the mile may be called that of ttj Wo , since a mile 
contains 63,360 inches ; the scale of 12 chains to the inch, or that of 
9 tot, signifies the same thing, because 12 chains contain 9504 inches. 
Conversedly, a Trench plan on the scale of - 4 - oooo is a plan on the scale 
of 1 inch to 40,000 inches. 

(9.) The selection of the scale at which a plan is to be made is not 
altogether arbitrary,'for it depends, on the one hand, upon the degree of 
accuracy required in the representation of the country, and on the 
other upon the dimensions of the paper at disposal. 

If we have to survey a distance of three miles, it is evident, that 
if our sheet of paper is only 24 inches long, we cannot employ a scale 




SCALES. 


5 


larger than 24 inches to 3 miles, or 8 inches to the mile; because, with 
a greater scale there would not be sufficient room to represent the 
whole of the ground. Any smaller scale, such as 4 or 2 inches to the 
mile, could be employed. 

Still, in employing a scale much smaller than that of 8 inches to 
the mile, we might meet with another inconvenience, since small objects 
could not be represented. The accuracy required must then guide us. 
At the scale of 1 inch to the mile, for instance, a field 10 yards in 
length would be represented only by rftr of an inch, a dimension much 
too small to be easily appreciated or represented. This scale is, there¬ 
fore, too small if we are expected to give every detail within 10 yards. 
What scale, in this case, should be adopted? In answer to this, let it 
be observed, that in supposing a plan to be mathematically true, we 
unavoidably commit in reading it an error due to the imperfection of 
our senses. We cannot appreciate a division smaller than the -iAo- 
part of an inch, for our eyes cannot perceive if the points of the com¬ 
passes are within rhy of an inch too near or too far apart. This 
uncertainty of reading becomes , -nro° > or 17 yards, at the scale of 
an inch to the mile. Therefore, if the plan ought to permit us to read 
every dimension within 10 yards, the scale should be such, that -rhy 
of an inch represents to the utmost 10 yards, or 1 inch represents 
1000 yards. To read within 35 yards, the scale should not be under 
■rro to 35 yards, or 1 inch to 3500 yards. 

When a plan is given, its scale at once shows with what degree of 
exactitude it can be read; thus, a plan at the scale of 4 miles to the 
inch gives us a distance on the ground within rh? miles, or 70 
yards. 

We have taken for granted that the part of an inch is the 
smallest dimension which we can appreciate, and, consequently, draw* 
although divisions of ^-g- of an inch can be obtained. In topographyj 
however, this accuracy becomes an illusion, for the paper on which 
plans are made contracts and expands so much under the influence of 
heat and moisture that the valuation of small dimensions depends 
upon the state of the atmosphere: -pro being already very small. 

(10.) In military surveys a great accuracy in the details is not 
expected, as it is not required to give very exact dimensions of 


6 


A PRACTICAL COURSE OP MILITARY SURVEYING. 


encampments, roads, &c. It is customary to employ the following 
scales:— 

24 inches to the mile for plans of a fortress of field works. 

12 inches for the plan of attacks on a fortress, of defensive 
positions, camps, &c, 

6 inches for the topography of a district, the march of 
armies , sketches of roads, encampments, &c. 

4 inches for larger surfaces, in reconnoitrings, &c. 

1 inch is adopted for the engraved sheets of the ordnance 
survey. 

In France the ordnance map is engraved at the scale of -owo* 

When smaller scales are employed, the plans are called maps, or 
geographical maps. 

Every plan or map should bear the name of the scale at which it 
has been made. 



CHAPTER II. 

TOPOGRAPHICAL DRAWING. 

§ I. 

Conventional Signs of Planimetry. 

(11.) A military plan sliould represent faithfully all the objects 
that possess some military importance or interest; such as— 

Communications: —railroads, high roads, cross roads, bridle paths, 
foot-paths; rivers and canals, with their accessories, such as dams, 
towing-paths, &c. Buildings , including houses, farms, castles, 
churches, &c.; they have a double importance as habitations and 
defensive positions. Enclosures :—walls, ditches, hedges, palisades, 
palings, &c., which constitute a cover and an obstacle for troops. 
Divisions of Culture: —ploughed lands, gardens, orchards, vineyards, and 
meadows, which produce food for men and cattle; woods, which furnish 
fuel and material to construct defensive obstacles with, and whose border 
itself is a capital line of defence; fallows, or uncultivated land. Besides 
these, all objects should be put down which, by their peculiar position, 
might serve to guide or rally troops, such as crosses, fountains, &c. 

(12.) The first condition which a military plan should fulfil is 
accuracy , the second, clearness, the third, simplicity. Since it is intended 
to serve for the combinations of the general, and for the movements of 
troops, it is very important that it should be as faithful as possible; 
and in order that all officers, even those who have no artistical turn, 
should easily draw and represent the various objects, and otherwise 
thoroughly understand a plan ready made, the conventional signs 
adopted to represent the objects alluded to should be clear and simple. 

(13.) Plates I., II., III.* and IY. contain the signs generally em¬ 
ployed. They are partly given by Williams’s Practical Geodesy, as 
the signs employed by the commissioners of tithes. Beginners should 
draw them frequently until they know them by heart; first in pencil, 
next in ink. On scales of 4 or more inches to the mile, every object 
is represented according to its real size, except trees, which are gene¬ 
rally made larger; but on small scales the roads and canals are made wider 
than they really are, because they would otherwise be scarcely visible. 


A PRACTICAL COURSE OF MILITARY SURVEYING. 


(14.) The plan actually executed on the ground, or “ minute ” as it 
is called, is done in pencil, and it is necessary to draw it carefully in 
case time should fail to ink it. This habit of making the pencil lines 
pure and strong will enable a beginner to survey more rapidly, and 
more accurately, inasmuch as he will not have to do twice the same 
operation, which often happens when, the minute being carelessly exe¬ 
cuted, some details are rubbed out. As soon as we return home we ink 
that minute with Indian ink, and, if possible, colour it. Should there be 
no time to ink a drawing, the pencil may be fixed by stretching the 
paper on a board, and washing it with a mixture of water and milk. 

(15.) Although the light is supposed to be vertical (22), it is usual 
to make an exception for rocks, buildings (when the scale is less than 
4 inches to the mile), water, woods, trees, and rivers when wide enough 
to be figured by two lines. Tor these objects we suppose the light 
coming at an angle of 45° from the left-hand corner of the plan. The 
thick lines render the plan more intelligible, by singling out, as it were, 
these objects, which are very important in a military point of view. 
(16.) With regard to colours, they are employed as follows 
Crops, yellow; Gravel, dots of burnt sienna over a wash of 
yellow ochre; Heath, purple; Marsh, horizontal light-blue patches 
running into green; Meadow ox Pastures, light green; Ploughed land, 
brown; River, dark blue; Road, burnt sienna; S'and, light-yellow 
ochre; Sandbanks under water, "as sand with a little red; Stone and 
brick buildings , carmine; Trees in masses, yellowish; Trees, single, 
dark green; Troops, colour of the uniform ; Water , blue, with shading 
on the shore; Wooden buildings, sepia. 

(17.) The list of conventional signs we have given is by no 
means complete, but it is quite sufficient for ordinary purposes. We 
might add a few military signs. 

Fig. 2. 


Artillery. 


Gavcilry. 



Infantry. 

Vidette. 


£3 Fort. 

)c( Redoubt. 
ttHH Abattis. 

~'M$M Chevaux de /rise. 

IfflMBB Rrakes or inclined palisade. 


Military pits. 

Passable. 

+ Impassable for Cavalry. 
=#> Impassable for Infantry. 


o Sentinel. 



CONVENTIONAL SIGNS. 


9 


When, however, objects are met with in a survey for which we do 
not know of any conventional sign, we make in the margin of the 
drawing a list of the peculiar signs we adopt for the occasion. 

(18.) We shall conclude this section by some hints on the drawing 
of conventional signs. 

Roads should always be drawn towards the draughtsman to insure 
to their sides an equal thickness throughout. The chief thing to keep 
in mind is the parallelism of these sides, as roads generally retain the 
same width except near the entrance of towns, where they widen, 
and in mountains, where they become narrow. The parallelism can 
only be obtained by drawing the left side first to serve as a guide for 
the right one. 

Railroads, being chiefly straight, are better drawn with a ruler ; the 
two sides should be exactly parallel and rather thick ; they are always 
narrower than roads. 

When two or more roads meet to form a crossing, the sides should 
not intersect at an acute angle, but should be rounded off. 

Rivers have the side nearest to the light made thicker. When 
wide enough they are filled with thin lines, parallel to the winding of 
the banks, kept closer near the sides. 

Lakes, ponds, and seas are drawn in the same manner, and the thin 
lines may be either horizontal or parallel to the shore. 

There are a great many ways of representing trees and woods. In en¬ 
graved plans (Plate XXXIII.) they are done as in the conventional signs. 
Sometimes on the sides of roads they are figured by thick dots. In 
sketches, woods are represented in patches somewhat as in landscape 
drawing, the light being, as usual, supposed to come from the upper, 
left-hand corner. 

Gardens are enclosed by walls or hedges; the interior is divided 
into small squares, with white spaces to figure the alleys, and the 
squares are filled with etchings. 

Buildings, when not coloured red, are filled with etchings, but on 
a scale less than 6 inches to the mile they are made quite black. 
When filled with etching, the sides farther from the light are made 
thick. 


10 


A PRACTICAL COURSE OF MILITARY SURVEYING. 


§ 11 . 

Representation of the Ground. 

(19.) When the ground is horizontal, the signs which we have 
given are quite sufficient to represent the country by the outline and 
relative position of every object; but when the ground is no longer 
level, new signs become indispensable to complete the plan, so as to 
mate it convey exact ideas of the hills, valleys, ravines, and other un¬ 
dulations of the surface. It is-most essential that, by means of such 
plan, an officer should at once be able to ascertain the position of com¬ 
manding points, and decide whether a spot is accessible or not to 
cavalry and infantry. 

A plan should therefore fulfil these two conditions :— 

1. Eepresent the ground so as to enable us to ascertain the relative 
height of the different points, and to judge of the nature of the 
slopes. 

2. Give a figure of the ground that will speak to the eyes. 

The first condition requires geometrical methods, whilst the second 
can only be obtained by combinations of shades. 

(20.) The geometrical method consists in supposing the ground 
intersected by horizontal planes : the projections of these intersections, 
or horizontal contours , are then transferred to the drawing at their 
reduced size. 

To understand the principle, let us make the experiment described 
in Burr’s treatise on surveying. 

Procure a stone somewhat resembling a hill, as may frequently be 
found ; fix it with clay to the bottom of a box provided with a plug¬ 
hole, and sufficiently large to leave a space free between the stone and 
its case. Pill the box with water stained with Indian ink, and let it 
off, by means of the plug, about a quarter of an inch in depth at several 
times, allowing sufficient intervals for the fluid to stain the stone in 
that plane, 4, 3, 2, 1, it has fallen to at the last abstraction. These 
stains will present a series of horizontal lines or contours, 4, 3, 2, 1, all 
round the surface of the stone; and if we examine the stone thus pre¬ 
pared, looking down upon the top, we shall see that the steepness and 


REPRESENTATION OE THE GROUND. 


11 


the flexures of its sides will be accurately marked by these contours, 
which might be said to form a scale of relative steepness. 

Fig. 3. 



The level of the water constitutes a horizontal plane, therefore 
those contours are the intersections of the stone by parallel horizontal 
planes. 

(21.) What is said of a stone may be said of a hill or of any surface, 
and those horizontal contours will give us a geometrical representation 
of the ground. 

But if we come to suppose the horizontal planes of section to be 
equidistant, we can at once, being given the-altitude of one point and 
the equidistance, find the altitude of any point. The inclination of 
the slopes may also be found by dividing this equidistance by the 
perpendicular common to two consecutive contours. 

A profile of the ground in any direction can also be obtained : the 
section of the ground along the direction a b, for instance, is found 
(Fig. 4) by carrying on any line c n, distances c a, c b, &c., respectively 
equal to a a, Ab, &c., and drawing through those points a, b, &c., 
perpendiculars representing the altitude of the contours a, b, c, &c. t 
the lines that connect the extremities of those perpendiculars figure 
























12 


A PRACTICAL COURSE OF MILITARY SURVEYING. 


the section. Elevations may also be drawn (see Plates XXI., XXII.) by 
the usual method of geometry. 


Fig. 4. 




By diminishing the equidistance, it is clear that the description of 
the undulations can beeome very accurate, and almost mathematically 
exact; it will therefore vary with the scale of the plan and the nature 
of the country surveyed ; the larger the scale, the smaller the equi¬ 
distance.* This method of representing the ground answers the 
first condition which a plan should fulfil, and is now adopted every¬ 
where for engineering purposes. 


* la the Irish survey of 6 inches to the mile, it was 50 feet for cultivated parts and 100 feet 
for mountainous and barren districts. In France, as a rule, the ratio between the equidistance and 
the denominator of the scale is constant, and = -gwo* an d a g rea t advantage is thereby gained, 
since at whatever scale a plan is made, the same inclination will always be represented by contours 
equally distant. At the scale ToUoo> the sections are thus 5 metres apart; at 2-5500, 10 metres, 
and so on. In exceptional cases only is this ratio altered. Thus, for the almost level plains of 
Champagne, the Ordnance Survey adopted the ratio ^55, giving an equidistance of 5 metres, at 
the scale 20000- 

























REPRESENTATION OF THE GROUND. 


13 


(22.) The second condition, as we stated, can only be obtained by 
combinations of shade; and if the conventions we adopt in order to 
gain this object are made to depend upon the principle of the horizon¬ 
tal contours, we shall obtain the very important result of combining 
accuracy with expression. 

Now, when we gaze upon the surrounding country, the effect of 
perspective presents to our eyes the apparent, instead of the real, 
forms ; the representation should therefore be made as viewed from a 
point vertically above ; but eyen then, if the sun is shining, the 
features will differ in the afternoon from what they were in the 
morning; and the effects of light and shade will not be in constant 
accordance with the true form. 

Tor these reasons we are led to suppose the ground illuminated by a 
vertical light, as happens in a cloudy day, and if, then, we imagine our¬ 
selves placed vertically above the surface to represent, we shall perceive, 
as in a model, that the more level a part the brighter it is, and the 
steeper the acclivities of a hill, the darker they appear. The shade is 
thus proportionate to the steepness of the slopes. 

(23.) This effect of shade might be produced by adapting the equi¬ 
distance to the scale and to the nature of the ground, so as to have 
contours close enough to give a shading; but the tracing of those con¬ 
tours on the ground would be too long for military purposes. If, on 
the other hand, we insert a sufficient number of lines between a few 
. contours determined by levelling, as in Plate VIII., the ground is not 
faithfully represented. The surface between two such contours has not 
always a uniform slope, and the space between two contours of the 
drawing would be a mean surface either enveloping or intersecting the 
real one. The execution would be tedious and difficult. 

Hence methods have been devised, some having regard to expression 
only, others combining expression with accuracy. We may classify 
them under three heads, the English system, the French system, and 
the German system. 

(24.) English systems are of two kinds ; the horizontal style and 
the vertical style, both of which have only expression in view. 

In the horizontal style the ground is figured by horizontal strokes 
more or less thick and close, and the altitude of the chief points is 


14 


A PRACTICAL COURSE OF MILITARY SURVEYING. 


given in figures. Plates IX., X., and XIX. illustrate two varieties of 
this method, which leaves a wide margin for artistical skill. 

At the Boyal Military College the horizontal method is now 
employed almost exclusively. Prom XI. to XVII. we give the series 
of progressive plates drawn by Major Petley for the instruction of the 
cadets. They are a most excellent imitation of nature, and there is 
no doubt that for military sketches this method is preferable to all 
others, on account of its simplicity and rapidity of execution. Plate 
XVIII., executed by Captain Bichards, Instructor in Military Drawing 
at Sandhurst, and formerly a pupil of Major Petley, is as good a 
specimen of a military sketch as could be wished for. 

There will, however, always be two defects in all the varieties of 
horizontal style. The roads, in hilly ground, deviate but little from the 
horizontal plane, and are not easily distinguished from the horizontal 
strokes to which they remain parallel. Again, the extreme strokes at 
the summit and base of a hill cannot be melted into the soft appearance 
of natural shade. 

(25.) In the vertical style the strokes are intended to represent the 
course which water would follow on its descent along the slopes; but 
in this country it has only been employed to obtain expression, and it 
is not more accurate than the other style, and requires more time. 
Plate XXIV. is part of the military sketch made in the Crimea by the 
officers of the Quartermaster-Greneral’s Department. Sometimes the 
vertical hachures are inserted between horizontal contours, but without 
any law and any regard to equidistance. 

Colonel Jackson, in his work on military surveying, very justly 
observes, “ that the uncertain application of conventional rules, such as 
regular plan drawing, does a vast deal of mischief; and there is great 
reason to regret that such a diversity of style should be tolerated in 
this country. Thus, when an extensive district is to be sketched, upon 
which several individuals are required to be employed, it becomes im¬ 
possible to unite their sketches so as to form a complete whole; nor 
can it be determined whose portion contains the most elevated ground.” 
The remedy is nevertheless simple enough. Let the Council of Military 
Education fix upon a system and recommend it to Sandhurst and 
Woolwich. 


REPRESENTATION OF THE GROUND. 


15 


(26.) In tlie French system the haclmres are traced perpendicular to 
the contours, so that the equidistance compared with the length of these 
hachures will at once give the ratio of the slope. The original contours 
must, therefore, be preserved on the plan, and the proper effect of light 
and shade is produced as follows:— 

M N, M' 1ST', (Fig. 5) being the contours given, the hachures a b, c d 


Fig. 5. 



are drawn at a distance, a c=c b; the square they form is then divided 
into two equal parts by a' b', and the rectangles a b', a'd arising there¬ 
from are again divided into two. By this process the hachures are at 
a distance from each other = ^ of their length, and in the practice 
the etching is thus expeditiously done. 


Fig. 6. 



•Should not the contours be parallel (Fig. 6) the hachures are 
drawn so as to meet them at right-angles. 

This, however, becomes difficult when the contours are far apart, 
and beginners will find it more easy to pencil intermediate contours in 
sufficient number to have them nearly parallel, and the hachures are 
afterwards kept at the proper interval. When the distance between 
the contours is very small, it becomes impossible to draw three 
hachures in the square; they are then made thicker and kept at 
equal intervals. The effect of shade they produce will thus harmonize 
with those of less rapid slopes. This should be done as soon as the 









16 


A PRACTICAL COURSE OF MILITARY SURVEYING. 


distance of the contour is less than about -jV of an inch, and the 
smaller this distance the thicker the etched lines should be. 


Fie. 9, 


Fig. 7. 




(27.) In order to preserve on the drawing the traces 
of the original contours, which are always useful to find 
altitudes, the hachures of a slice should not be the con¬ 
tinuation of those above (A), but should be made to 
correspond to the intervals of the slice immediately 
above ; and to avoid the bad effect (B) produced by 
lighter spots, they should be exactly terminated at the 
contour (C). (Fig. 8.) 


Fig. 8. 





(28.) In order to secure an uniform scale of shade 
for all plans, scales of thickness or diapasons have been 
adopted. In the diapason of the Ordnance Map the 
ratio of black to white is (Fig. 9) equal to the tangent 
of the slope multiplied by f. For a slope of 45 degrees 
the proportion of black to white is thus 3:2. All 
slopes steeper than 45° are represented as escarpments. 

The French system, we have said, combines accuracy 








































































DEFINITIONS. 


17 


witli expression, but is not expeditious. The horizontal style, on the 
contrary, sacrifices accuracy to expression, and is expeditious: its defect 
might easily be remedied by representing the original contours by 
strokes and dots, either as in the annexed diagram, or in some similar 
way. Tor engraved map, however, the vertical style will always be 
preferable. 


Fig. 10. 



(29.) In the German system the liachures are also perpendicular to ' 
the normal contours with or without reference to their equidistance. 
In the system of Lehmann, no regard is paid to the equidistance, and 


Fig. 11. 

























































18 


A PRACTICAL COURSE OP MILITARY SURVEYING. 


the slopes are measured by the angle they form with the margin. The 
diapason of Lehmann gives, therefore, the length and thickness of the 
hachures from 5 to 6 degrees up to 45 degrees. The latter slope, being 
impracticable to armies, he represents by absolute black. The ratio of 
black to white is equal to the ratio of the angle of a slope to its 
supplement to 45 degrees. Thus, for the slope of 35 degrees, the 
thickness of the hachures is so regulated as to give a tint in which the 
black is to the white as 35 :10 or 7 : 2. In this method the features 
of the ground are strongly marked, but the tints are too dark, and it is 
often difficult to read the small writing and see the details. 

In other German diapasons the maximum of shade is taken for 60 
degrees, but these methods requiring the measurement of every angle 
are too long in practice. 

(30.) Besides these three systems, there are other methods of shading 
hills. Brushing with Indian ink is one of them; but it is not sus¬ 
ceptible of great accuracy, and is only employed for rough sketches. 

To give more accentuation to the features, oblique light has been 
had recourse to, but it is impossible to represent the real steepness of 
a slope, since the same slope may be placed in a thousand different 
positions as regards the direction of light: hence the same slope is dif¬ 
ferently shaded: it must also be observed that the horizontal surface 
has to be shaded, and the effect is no longer natural. 

Plates XXY. and XXYI. are* examples of shading extracted from 
the course of Mr. Bardin, lately Professor of Topography at the Imperial 
Polytechnic School of Prance. 

Perspective has also been tried in combination with a horizontal 
projection, as may be seen in old plans (Plate XXYII.), but this 
method of bird’s-eye view drawing is too inaccurate, and it is now con¬ 
fined to those popular maps which are published for the million in 
time of war. 


19 


$ III. 

Features of the ground. 

(31.) The undulations of the ground may be reduced to a few fun¬ 
damental forms, whether we consider a large extent of the earth’s sur¬ 
face or a small area. Looking at a continent or an island, we observe 
that the ground rises from the shore up to a chain of mountains, which 
separates the whole surface into two general slopes or zoatersheds. Each 
of these watersheds is subdivided into secondary surfaces by chains 
either perpendicular or oblique to the first. The declivities of the ad¬ 
jacent chains include between them a valley. In the same manner the 
branches running from these chains contain valleys of less dimensions, 
shedding their waters in the principal valley; while they themselves 
receive the tributaries of the concave surfaces formed by the minor sub¬ 
divisions of the branches. The ensemble of all the valleys which empty 
their water into the sea by the same mouth constitutes what is called 
a basin. 

(32.) The chains of mountains vary much in character. Some¬ 
times the two declivities of a watershed meet on a line well defined or 
crest; sometimes they are connected by a flat surface at a greater or 
less altitude, called table-land , or they may be united by two counter¬ 
slopes, enclosing lakes without outlets. 

(33.) The crest of a chain or watershed-line is generally formed of a 
series of summits, between which depressions, more or less deep, estab¬ 
lish communication between the opposite sides, forming what is called 
a col or pass. 

A col, properly speaking, may he defined the highest part of the 
intersection of two convex surfaces; it is therefore the origin of valleys, 
and is horizontal. 

c 2 


20 


A PRACTICAL COURSE OF MILITARY SURVEYING. 


Fig. 12. 



When the col is long and the adjacent heights steep, it becomes a 
defile. The defile, however, may also be found along the base of 
mountains. 


Fig. 13. 



(34.) The name of hills applies to mountains of minor elevation, 
more or less conical, and without any apparent crest. 


Fig. 14. 



Counterforts (croupes) are indentures found in ranges of hills ; their 
flanks belong to two adjacent valleys. 







FEATURES OF TIIE GROUND. 


21 


Fig. 15. 



(35.) A valley is the concave surface formed by two declivities or 
flanksj the line m ml of less inclination according to which the slopes 
meet is called the thalweg. 

Fig. 16. 



When the thalweg is but slightly sloping the valley becomes a 
dale. 


Fig. 17. 


















22 


A PRACTICAL COURSE OF MILITARY SURVEYING. 


When the flanks are very steep and close they form a ravine . 


Fig. 18. 



In Plate V. we have combined these chief undulations :—thus 
A, a, a, a, are cols ; Gr, Gr, defiles; B, B, b, b, hills ; C, C, C, counterforts ; 
D, D, valleys; E, E, vales; F, F, ravines; H, H, table-lands. 

(36.) In drawing the hachures between the horizontal contours, we 
should pay attention to the following remarks :— 

The extreme hachures of a slope should be terminated as fine as 
possible, in order to render softer the melting of the shade into the 
white of the paper, this conformably to nature, where we see no slope 
beginning or ending abruptly. 

No hachure should be drawn on the direction itself of a thalweg or 
a watershed-line, because a continuous line would strike the eye un¬ 
naturally, as those directions have the least inclination. For a similar 
reason, in ravines the extreme hachures of the flanks should not meet, 
but should end in a fine point. 


Fig. 19. 



In a col the little horizontal table-land is left in blank, and it is 
limited by drawing the intermediary contours mn, mq, qp, pn (Fig. 19) 












COPY AND REDUCTION OF PLANS. 


23 


on which we arrest the point of the extreme hachures. (See Plates 
XX., XXI, XXII, XXIII.) 

(37.) With the rules laid down we are enabled to figure precisely the 
forms of the ground, since the direction of the hachures indicates that 
of the slopes, whilst their length or distance compared to the equidis¬ 
tance permits us to measure the real inclination of the latter. The 
acclivities have been divided into three classes: those practicable for 
carriages and inclined to the horizon at not more than 15°; those 
practicable for cavalry limited to 30°; and those practicable only for 
infantry and limited to 45°. From what precedes, the student will 
easily perceive on a plan to which class belong the various undulations 
thereon figured. When the length of the hachure is less than 3 or 
4 times that of the equidistance, the slope is no longer passable for 


Fig. 20. 



artillery. When it is less than twice the equidistance, the acclivity is 
too rapid for cavalry, and when both lengths are equal, we know that 
it is the steepest slope practicable for infantry. 


§ IV. 


Copy and Reduction of Rians. 

(38.) The first step in Topography is to become thoroughly 
acquainted with the drawing of plans, a knowledge only acquired by 
practice. Copying plans ready-made renders one familiar both with 
the conventional signs and with the ordinary features of the ground. 
This part is the most difficult; but once mastered, surveying becomes 
comparatively easy. 

(39.) When a plan is to be copied on the same scale, its surface is 
divided into squares or rectangles (Plate XXXI.), which will be so much 
the smaller as the details will happen to be more minute. An equal 
frame is then drawn, and its surface is divided into the same number 
of squares as the model (Plate XXVIII.). The details are then copied 



24 


A PRACTICAL COURSE OF MILITARY SURVEYING. 


square by square. It is advisable to avoid the use of compasses, and 
to transfer everything at sight, for it is the only way to learn how to 
draw rapidly and accurately. Should a square contain too many 
details, the diagonals may be drawn to give further assistance, or its 
surface may be subdivided into smaller squares. If the model must 
not be soiled, we cover it with glass, and trace the square on the glass. 
We begin with the pencil and draw the roads, rivers, buildings, walls, 
gardens, rocks, hedges, &c.; then we ink these details in the following 
orderroads, rivers, buildings, walls, footpaths, gardens, ditches, 
direction of hedges, divisions of culture, and rocks. 

When this is done, we trace in pencil the horizontal contour 
(Plate XXIX.). Next we shade the hills, either in the horizontal or 
vertical style (Plate XXX.). The copy is afterwards completed by 
figuring the woods, marshes, meadows, or colouring them, as the case 
may be. The names are then written, together with the altitude of 
the chief points, and the scale is either made or named under the 
frame. 

(40.) If the copy is to be made on a different scale, say twice 
smaller, a frame is drawn with sides twice smaller than the model, and its 
surface is divided into the same number of squares. We proceed then as 
before, with this exception, that we copy one contour out of two, three, 
four, &c., when the new scale is twice, three times, four times, &c., 
smaller. 

(41.) If the area of the copy must bear a certain ratio to that of the 
given plan, say m : n for instance, we proceed as follows :—Draw the two 


Pis. 21. 



lines C D, D B, so that (Fig. 21) C D : D B : : m : n. On B C describe a 







COPY AND REDUCTION OF PLANS. 


25 


semicircle, erect D A perpendicular to B C, then AC': AB ' : : m:n. On 
the direction A B take A H equal to the side of the model, draw 
through H a parallel to B C, and A K will be the corresponding side 
in the copy. The second side will be found in the same manner. 

* Having then traced the frame, we divide its surface in the same 
number of squares as the model, and proceed as usual. The scale of 
the copy is easily obtained. Take A C' equal to one inch, draw C' B' 
parallel to C B, and the distance A B', measured on the scale of the 
model, will show what one inch represents in the copy. 


26 


CHAPTER III. 


TRIANGULATION. 

(42.) We have said (6) that planimetry consists in making a reduced 
image of the projections of the various points of the surface of the 
ground. In practice, however, we make a selection among these points, 
and begin by considering Only the chief ones, such as steeples, 
chimneys, isolated trees, and other objects easy to recognise at all times, 
and we imagine them united by straight lines. The’projections of those 
lines constitute a series of triangles forming a sort of netting (canvas) 
(Fig. 22), between the sides of which all the other details are contained; 


Fig. 22. 























TRIANGULATION. 


27 


and the first problem of planimetry, contained in the 18th proposition 
of Euclid (lib. vi.), will be to make a figure similar to that canvas, an 
operation called triangulation: the second problem will again he to 
make figures similar to those contained in these triangles, an operation 
called the filling in of details. 

Thus, the points a, b, c, d, being projected in a, b, c, d, on the 
horizontal plane (Fig. 22), the figure a b c d is called the canvas, and 
all that is contained in every one of the triangles, a b c, c b d, &c., 
constitute the details. 

It is readily understood that the triangles of the canvas must be 
more or less numerous according as the scale of the plan is small or 
great, so that the details they contain may be represented afterwards 
in their relative positions without any appreciable error. 

(43.) Since, to construct a triangle, we require to know either three 
sides, or two sides and one angle, or one side and two angles, it follows 
that three different methods may be adopted, to make a survey. In 
military topography, however, where expedition is a most essential 
condition, the methods founded upon the measure of three sides, or of 
two sides and one angle, are rejected as too long, and the following 
process is preferred (Fig. 23):—A side, a b, is first measured ae¬ 


rie. 23. 



curately, and its projection is drawn at the scale in a b; then in 
observing the angles cab,abc, the elements of the triangle abc are 
obtained and a b c is constructed on a b, similar to a b c. The 
sides a c, b c, being thus known, we go on measuring the angles 



28 A PRACTICAL COURSE OF MILITARY SURVEYING. 

d a c, a c d, and the triangle a c d is made similar to acd. Again, 
the angles c d e, e c d, furnish the triangle c d e; and so on, measuring 
the angles. 

This line, a b, the only one we measure, is called the base. It is 
selected, as much as possible in the middle of the surface to survey, 
and such that from its extremities several important points may he 
seen. In that manner several angles may be observed at a same 
station: thus while at a, the angles b a c, c a d, d a h, h a b, b a b, 
are measured. 

(44.) The form of the triangles is not arbitrary, they should be as 
nearly equilateral as possible, for if an angle were very acute the 
slightest error in the measurement of the others, in a for instance 
(Fig. 24), would cause a great difference in the position of the vertex 


Fig. 24. 



c. Besides, it is very difficult to see exactly where two lines meet at 
so small an angle. The equilateral form possesses the further advan¬ 
tage of covering a given surface with a less number of triangles, and 
thereby simplifying the labour. 

(45.) The maximum length of their sides, as well as that-of the 
base, depends upon the approximation with which the angles are 
measured, and upon the scale adopted. The students acquainted with 

trigonometry will find the length by means of the formula 1= ^ ^ - 

in which 1 represents the length, and e the error depending on the scale 
or uncertainty of reading (9), and a the error committed in observ¬ 
ing the angles, varying with the instruments employed. We give 
a few results at the end of the chapter. 

(46.) Starting from a base, we have said that we draw triangles 
similar to those of the ground by means of the angles: this can be 
done either by calculation or construction. Trigonometry enables us, 
when knowing two angles and one side, to calculate every dimension of 
a triangle. Having, therefore, measured the base and all the angles, we 






TRIANGULATION. 


29 


can calculate all the sides, and then draw them at the scale by the 
process of geometry. But this method, certainly the most accurate 
for surveys of importance and precision, is altogether set aside in 
military surveys on account of the time it requires. The second 
mode, which is the one that should be adopted, consists in laying 
down or.protracting the angles as soon as they are measured. 

(47.) We need no field-book to write down the various measures, 
as is often recommended, but we at once draw or plot, as it is called, 
what we observe. The only book that we may carry will serve to take 
note of the statistical, political, and military information (139) which 
we require. 

Let it be remembered that it is only by plotting on the ground 
itself that an officer will acquire the habit of sketching rapidly the 
features of a country. In one case only (122) may we take notes of 
some measurement; but even then it is not indispensable. 

When the canvas has been plotted, the details are filled in by a 
similar process, viz., by measuring distances and angles; and it is there¬ 
fore logical that we should successively determine upon the instruments 
destined for that purpose. 


Error in the Angle. 

Scale—Number of Inches 
to the Mile. 

Maximum Length 
of Sides in Yards. 



'2 . . . 

15126 

V . . . 

> m 

4 . . . 

7563 



,6 . . . 

5042 



[2 . . . 

1008 

15' . . . 

. . 

4 . . . 

504 



6 . . . 

336 



2 . . . 

504 

30' . . . 

. . 

4 . . . 

252 



6 . . . 

168 



(2 . . . 

252 

1° . . . 


4 . . . 

126 



(6 • • • 

84 













30 


CHAPTER IV. 

DISTANCES. 

(48.) A chain, or a rope, 100 feet long, divided into a hundred links, 
together with a set of 10 arrows, is sufficient to measure every distance 
in a survey. 

Two persons, the leader and the follower, are required to take the 
measure. The leader starts with the arrows in his left hand, and one 
end of the chain in his right, while the follower, remaining at the point 
of starting, directs the leader in the proper line and makes him stretch 
the chain. The leader then plants an arrow, and starts afresh as 
before, whilst the follower comes up to the first arrow. The second 
arrow is planted by the leader, and the first taken up by the follower; 
and so on. When the 10 arrows have been used, the distance 
measured is equal to 10x100=1000 feet, which are noted, and the 
follower returns the arrows to the leader to continue the operation. 

The chain should be kept as horizontal as possible, since the 
measure required is that of the horizontal distance. When the 
ground is not level, the chain being kept horizontal, the effect of 
gravity will curve it a little, therefore shorten its length, and the dis¬ 
tance measured will be too great. It is, therefore, better to put the 
chain flat on the ground and to reduce the distance thus found to the 
horizontal plane. The chain used by civil engineers, or Gunter chain, 
is only 22 yards long. It is very convenient where the contents of 
an estate are to be given in acres, because ten chains in length by one 
in breadth measure exactly one acre. 

(49.) Pacing is generally resorted to, while filling in the details of 
a survey (52). The trotting of a horse might also (53) be made 
available. 

Distances can also be measured by time, when we have previously 
ascertained over how many yards we walk or ride in a given time. 


DISTANCES. 


31 


This is not of rare occurrence in the field. When distances are measured 
by pacing or riding, a correction is necessary, owing to the lengthening 
caused by the acclivities, and the turnings of roads : on slightly uneven 
ground we subtract -f of the distance found, and ± when the undulations 
are more important. 

When the atmosphere is calm, sound travels at the rate of 1118 
feet per second, therefore, a musket fired may serve to measure a dis¬ 
tance ; a watch gives the number of seconds elapsed between the 
instant the light is seen and that when the report is heard: that 
number multiplied by 1118 feet gives very approximately the distance. 

If no watch is to be had, the time is obtained by counting the 
pulsations of an artery. A sound s pulse averages from 75 to 80 in 
a minute. 

Distances may even be guessed by observing that in clear weather 
the windows of a house can be counted at 4000 yards. Horses and 
men appear as dots at 2200 yards, a horse is clearly seen at 1200 
yards, the movements of men are perceived at 800 yards, and the head 
is distinctly visible at 400 yards. 

Several instruments, known under the name of “ stadia,” have been 
constructed for the purpose of measuring (^stances; but as the means 
explained above are amply sufficient for all military surveys, we shall 
not enter into their description, and we refer the students to any 
treatise on mathematical instruments. 

(50.) The distances once measured must be drawn at the scale; 
we must therefore illustrate, by a few examples, how to construct 
one. 

Let us begin with a scale of 6 inches to the mile. 

Since 6 inches represent 1760 yards, 1000 yards will be represented 

by or 3*4 inches. If, therefore, we take a line 3'4 inches 

long, and divide it into ten equal parts, each part will represent 100 yards; 
if these parts are farther subdivided into ten, each new subdivision 
will represent 10 yards. To construct the scale, draw in pencil three 
parallel lines, about Ar of an inch apart, and mark off on the bottom 
line a b=3’4 inches. Divide a b into ten parts. This is done by 
drawing through a a line a o, making with a b any angle, marking 



32 


A PRACTICAL COURSE OF MILITARY SURVEYING. 


off any length a c, and taking it ten times from a to c : joining c b, 
and through the points of divisions c 8 , c P c 6 , &c., drawing parallels to c 
b, these will divide a b into ten equal parts. Produce a b to the left, 


Fig. 25. 

Scale of Six Inches to One Mile. 



take a b equal to one part, and by the same process divide it into ten. 
Ink the two bottom lines ; through the points of division draw perpen¬ 
dicular to them, limiting their lengths to the top line for the primary 
divisions, and the middle one for the subdivisions; number the 
divisions, and write on the right the unit of measure which in this case 
is “yard.” 

This scale is used on thp paper, by means of a pair of compasses, as 
we would employ a chain or a yard. Suppose we want to take off 
470 yards ; place one point of the compasses on division 400, and the 
other point on the 7th subdivision: the length included between the 
two points is 470 yards. Conversely, to value a dimension of the 
drawing, take it with the compass, place one point on the division 0, 
and read the figure corresponding to the right point. If this point 
does not fall exactly on a division, move it to the left until the right 
point coincides with the nearest division, then the left point will mark 
the required subdivision. 


Fig. 26. 

Scale of Six Inches to One Mile. 

to 5 o to 20 30 to so ch ains 

Li_i..r. iJ.o.'irv'.i.. .. I I I 1 I 

If the chain of 22 yards is the instrument actually employed to 
measure the distances on the ground, it is preferable to construct the 
scale of 6 inches to the mile as follows (Tig. 26) :— 







SCALES. 


33 


Since 6 inches represent 1760 yards or 80 chains, therefore, 60 

chains=^-g^=4’5 inches. Take a length of 4’5 inches, divide it into 

six equal parts; and if we subdivide the left part into ten, we shall 
have subdivisions representing single chains. 

To construct a scale of 2 inches to the mile. In this case we can¬ 
not show parts representing 10 yards each. Since 2 inches correspond 

to 1760 yards, 4000 yards are represented by =4'54 inches. 

Divide this length into 4 parts (Fig. 27), they will show 1000 yards: 
dividing into 10 we have subdivisions of 100 yards. 

Fig. 27. 

Scale of Two Inches to One Mile. 

tooo 5oo o iopo 3000 3000 vards 

I i i ' ' 1 ' ' i ' I ■■ -]- ■ - . - - I ■ H * 


(51.) To construct a scale 4 -<rb-o-, we find that a distance of 3000 

yards is to he represented by " o^qqqq ^ = 5'4* inches (Fig. 28). Divide 

the length into three parts, we shall have divisions of 1000 yards, and 
subdivisions of 100 yards. 

Fig. 28. 

Scale of 2^ oq . 

■>o_ _ $oo o _ *dqo _ 2oooyanfa 


(52.) Should the distance be measured by pacing, a proper scale 
must be constructed. Although the length of a pace is not a constant 
magnitude, we may assume that in general 2000 paces make up a mile. 
If the plan is to be made on a scale of 4 inches to the mile, then since 
4 inches represent 2000 paces, we shall have divisions of 100 paces 

Fig. 29. 

Scale of Four Inches to One Mile. 

noso a too 200 m 4 M eop m m m sop m isooptuxs 

Uml I 1 4 1 -I—I—1—1 -1-1—1 1- 1. 1—1—Izd--— I-1—1 

(Fig. 29), and subdivisions of 10 paces, in dividing these 4 inches 

D 











34 


A PRACTICAL COURSE OF MILITARY SURVEYING. 


into 


j* 

I 

1 

til 


*- 

os- 


twenty parts, and subdividing one part again into ten. If 2000 of 
our paces do not make a mile, we can ascertain 
bow many do by walking over a distance which has 
been measured. 

(53.) Scales are also made for distances mea¬ 
sured by time. 

Suppose, for instance, that we employ either 
the pace, the trot, or the gallop of a horse, and that 
we want to construct a scale of -nrwo. We first 
ascertain at what' rate our horse proceeds: in 
general a horse goes over 100 yards walking, 180 
yards at a moderate trot, 230 yards at a fast trot, 
and 280 yards at a gallop in one minute. 

"We then calculate that in walking 20 minutes 
the horse goes over 2000 yards, a distance repre- 


Fig. 30. 
Scale of 16 S 0 q . 

j? 


8 

I 




v- 


wl 


t 




sented by 


2000x36 


=4*8 inches ; that at a moderate 


15000 

trot and fast trot he goes in ten minutes over 
1800 and 2300 yards respectively distances repre¬ 


sented by 


2800x36 


=4 - 3 and 


2300x36 


= 5*5 inches; 


15000 15000 

and that at a gallop he makes 2800 yards in ten 
minutes, or 1400 in five, a distance represented by 
33 inches. These lengths, 4‘8, 4’3, 55, and 3*3 
being respectively divided into twenty, ten, and 
five parts, will give us parts representing one 
minute. 

(54.) In examining foreign plans it is found 
very useful to construct for them a scale in 
English measures. Suppose that it is a French 
plan, the unit of measure of which is the metre. If 
the representative fraction of this plan is given, 
we have only to proceed as in a former example (51); 
but if this fraction is not given, we take ofi* on 
the scale any distance, say 1000 metres. Let 
that distance measure 3*9 inches, then we know 














DISTANCES. 


35 


that 3‘9 inches represent 1000 metres (Fig. 31), or 1000 x3’28 English 
feet =3280 feet =1093’33 yards. It is now easy to find that 1000 

yards are represented by ^ j ^, - |g- = 3'56 inches, and we proceed as in 
former examples. 

Fig. 81. 

ioo so o mo soo 300 400 soo goo no goo aoo 1000 metres 

bx jx Li.nl—1.,. ,L I ),, 1 ,L- 1 —- | - 1 ... | = J 


IOO SO O IOO 200 OOO 400 


ioo soo soo 
-i——1 -zr-L 


loop-yards 


(55.) It has been said before (48) that the distances obtained from 
direct measurement on an inclined ground should be reduced to the 
horizontal plane, inasmuch as their projection only is required. For 
the student familiar with trigonometry, this reduction offers no diffi¬ 
culty, since the projection is equal to the distance measured multi¬ 
plied by the cosine of the angle of inclination. As tables of sines 
are not always at hand, we give here the reduction ready made. 
(See 115.) 


DISTANCE ACTUALLY MEASURED 100 YARDS. 


Angle op Inclination. 

Distance Reduced. 

0°. 

.... 100 

5. 

.... 99-6195 

10. 

.... 98-4808 

15. 

.... 96-5926 

20 .. 

.... 93-9693 

25. 

.... 90-6308 

30. 

.... 86-6025 

35. 

.... 81-9152 

40. 

.... 76-6045 

45. 

.... 70-7107 


(56.) Two points determine a direction, but when they are some- 
d 2 




















36 


A PRACTICAL COURSE OF MILITARY SURVEYING. 


what distant, it becomes a difficult matter to measure along that 
direction, unless it be properly traced or signalled. We shall therefore 
begin with the following problem :— 

To mark on the ground the direction between two given points , 
A and B. 

1st. If one of these points, A, is accessible, an observer takes 
his station at it, whilst another (Fig. 32), C, plants staves in the 


Fig. 32. 



direction of B, so as to make them coincide with the vertical of B, 
which is ascertained by A, who signals to C with the hand until 
the coincidence takes place. 

2nd. If the direction between A and B is to be produced, we place 
a staff in C where the vertical of B masks that of A. (Fig. 33.) 


Fig. 33. 



A B C 


3rd. If both points are inaccessible. (Fig. 34.) 

When neither point is visible from each other, two observers, a and 
b, place themselves out of the direction A B, facing each other: b 


Fig. 34. 



makes sign to a to move until he is in the dressing b A; then a puts in 
a similar manner b in the position 1/ where he masks B: again, b' 
moves a to a' on the direction b' A; a' in his turn places b' to b"; and 







DISTANCES. 


37 


so on. In this manner a moment arrives when both persons respectively 
conceal from one another’s view the points A and B: when such is the 
case they plant staves, and proceed as before. 

If both observers are too far apart to perceive each other’s signs, b 
places himself in the direction a A; a facing b marches towards A B; 


Fig. 35. 



and b, by more rapid motions, keeps himself in the dressings a' A, 
a" A, &c., until he conceals B from the sight of a. Then all the points 
A, a' v , b' v , B, are in a line, and staves are planted as before. 

Although a military survey should he executed according to the 
principles laid down in the former chapter, yet, as we may fail to 
obtain proper instruments to measure angles, it is well that an officer 
should understand to what advantage he can turn a mere chain (or his 
pace), and the following examples will familiarize him with that 
simple instrument:— 

(57.) To trace on the ground a perpendicular to the extremity , A, of a 
line , A D, which cannot be produced. 


Fig. 36. 



ij 


Let any point, C, be taken; chain or pace C A; trace the line 
C H = C A. Produce C H (56) and make C B = C H. 

The line A B is the perpendicular required. 

A simple process for setting off a right angle on the ground consists 
in making a triangle with three pieces of cord of the respective lengths 







38 


A PRACTICAL COURSE OF MILITARY SURVEYING. 


3, 4, 5, or in this proportion, placing the side 4 on the direction, A B, 
with which the angle is to be made, and stretching the other two until 
they haul together on the ends of side 4, the side 3 will give the 
direction at right angle with A B. 


Fig. 37. 



(58.) To find the distance between two points , A B, one of which, A, is 
inaccessible. 

Produce A B to any point, C: through C trace C D in any direc¬ 
tion, and bisect it in E with a staff; join E B and produce it to E, so 

Fig. 38. 


A 



as to make E E=E B. Join D E and produce it to Gr, where E is seen 
to coincide in direction with A. Then E G=A B. 

The value of A B could be found in a different manner. 


Fig. 39. 






DISTANCES. 


39 


Set off B D at right angle with A B, and make it equal to 4 
yards; take DC = 1 yard; plant a staff in C; set off D E at right angle 
with D B, and mark on it the point E at which C and A are seen in a 
line. Then D E = 4 - A B. If the distance, A B, is great, instead of yards 
take chains. 

(59.) To make an angle equal to a given angle, B. 

On the sides of the angle B measure the distances B A, B C; trace 
B C and measure it also. Now, if the distance B C be carried on the 


Eig. 40. 



line with which the angle is to be made, on M N for instance, and 
circles be described from the centres M and N with A B and A C 
respectively as radii, the circumferences meet at a point P, and 
angle P M N=A B C. 

(60.) Through a given point, C, to draw a line parallel to a given line, 

AB. 

In A plant a staff, measure the length of its shadow, A D, and also 
the lines A B, B D. Bepair to C, plant there the same staff or one 


Eig. 41. 



E 


of equal length, and on its shadow, C E, construct the triangle 
C E T=A D B. CP is the parallel required, 






40 


A PRACTICAL COURSE OF MILITARY SURVEYING. 


If there is no sun, or if both points A and B are inaccessible, take any 
point, D, on the direction C B ; measure C D, D B (58); produce A D, 
and on it measure D H, having to AD the same proportion as C D has 
to B D : C H will be parallel to A B. 


Fig. 42. 



(61.) To produce a direction , A B, beyond an obstacle. 

Take any point, H, trace the line B H, and also two other direc¬ 
tions, H C, H D, on the other side of the obstacle. 


Fig. 43. 



H 


Mark any point, F, in H B, and measure H F and B F. Through 
F trace F M parallel (60) to A B. Measure H G and H M. 

Now, if G C and M D are made the same multiple of H G and 
H M as B F is of F H, then C I) is in the same line as A B. 

When measuring along a direction A C, if an obstacle is in the way 
(Fig. 44), from B measure a line B E, in any direction ; bisect it in G; 
measure G D, produce it to H, making G H=G D. The line E H is 
equal to B D. 







DISTANCES. 


41 



(62.) To find the aisiance between two inaccessible points, A and B. 

If any point, C, on the direction A B is accessible (Fig. 45), set off 
the perpendicular C D and take on it the distance D E, a known part. 
Trace M N perpendicular to C D, and on it mark the points M and N 
in a line with E B and E A; M N shall be the same part of A B as 
DEis of EC. 

Fig. 45. 



If there is no point accessible between A and B (Fig. 46), take any 
point, C. Measure the distances C A, C B (58). Take C D an exact 

Fig. 46. 



fraction of C A, and C E the same fraction of C B. Measure I) E ; it 
shall also be the same fraction of A B. 

(63.) To bisect an anqle . 









42 


A PRACTICAL COURSE OF MILITARY SURVEYING. 


If the vertex is accessible, from it as centre describe a circle, measure 
the chord A B, bisect it in 0 ; C 0 shall bisect the angle. 


Fig. 47. 



If the vertex is inaccessible (Fig. 48), trace any line, A B. Measure 
the angles CAB and C B A, take half their sum, and construct angle 


Fig. 48. 



CAB equal to it. The middle, 0, of A D belongs to the line that 
bisects the angle C. 











DISTANCES. 


43 


If tlie angle itself is inaccessible (Fig. 49), mark any two points, E 
and D, on the direction of the sides. Through D trace D Gr parallel to 
C E; measure equal distances, produce 

C E produced in I. Bisect H I in 0: the line 0 
angle given. 

(64.) To determine the direction of the capital of 
inaccessible ivoric. 


Fig. 50. 



H Gr till it meet 
0 shall bisect the 

a bastion or of any 


Trace any line, M N, cutting in M and N the prolongations of the 
faces. By means of the chain (63) bisect the angles CMN, ON M, by 
M C', N C'. These two lines meet in O', which belongs to the 
capital. 

(65.) To find the height, A B, of a building. 

Plant a staff, D E \ find the position of the point 0, where the eye 

Fig. 51. 

B 


o— 

must be placed to perceive D and B in the same line with it. Measure 
E 0, 0 A, and DE. A B shall be the same multiple of D E as A 0 
is of BO. 

Many other methods may be resorted to for finding the height of a 
building, but the most simple consists to compare the length of its 






44 


A PEACTICAL COUESE OF MILITAEY SUEYEYING. 


shadow with that of a pole of known height; the ratio of the two 
heights is the same as that of the shadows. 

Fig. 52. 



(66.) lo fix on apian the projection of a point, having on that plan the 
projection of two lines. 

If the point X must he on both directions (Fig. 53), it is evident that 
its projection is at once obtained by producing the projections of the 
lines till they meet. 

Fig. 53. 



If X is on the direction of only A B (Fig. 54), produce C D on the 
ground till H measure H X, and draw h x at the scale on the plan. 


Fig. 54. 




If X is on neither direction (Fig. 55), march along C D till you 
arrive at 0 on the direction B A. Measure 0 X and C X. On the plan 
the triangle o c x at the scale. 








DISTANCES. 


45 


Fig. 55. 




(67.) To fix in a plan the projection of a point, X, having on that plan 
the projection of a line, A B, on which X stands, and also that of an 
accessible point, C. 


Fig. 56. 



March on direction C X; measure it. On the plan, from point c as 
centre and distance, C x reduced at the scale, describe a circumference: 
it shall meet a b in the point x required. 

If X is not on direction A B (Big. 57), measure C X and X H. On 



Fig. 57. 



the plan determine as above the point h, and carry H X at the scale 
on h x. 

(68.) Two points, A B, being given, to fix on the plan the projection of 
a third, X, which is inaccessible. 






46 


A PRACTICAL COURSE OF MILITARY SURVEYING. 


Trace the directions A X, B X, and measure A B, A D, D B, A E, 


Fig. 58. 




E B, and at the scale construct the triangles a d b, e b a; the intersec¬ 
tion of the lines ad, eh, fixes the position of x. 


Figs. 59 and 60. 



If an obstacle (Figs. 59 and 60) prevents from moving from A 
to B, measure any two triangles, A D 0, B F H, and proceed as above. 

If the point A itself is inaccessible, (Fig. 61), measure B 0, produce 
C X to any point, D, forming with C and B a proper triangle, and on 
the plan construct the triangle d b c at the scale. On the ground, 












DISTANCES. 


47 


produce BD to H on the direction X A, measure D H, and carry it 
on the plan on d h; ha and c d produced determine the point X. 


Fig. 61. 



(69.) To find the projection of several points, ABC. (Fig. 62.) 
Measure a base, D B; from D and E as centres, and radii D K, L E, 

1?IG. 62. 



describe two circumferences; measure the chords K F, KG, KH and 
L M, L N, L P. On the plan draw the base at the scale onde; describe 
the circumferences with radii d k, 1 e; and by means of the radii k f, k g, 
kh, lm, In, 1 p, complete the triangles dhk, dgk, dfk, el p, elm, 
el n. The other sides produced determine the projections a, b, c. 

(70.) A great number of instruments have been constructed to 
measure angles, but some are difficult to adjust and cumbersome to carry ; 
we shall therefore confine ourselves to those which an officer can easily 








48 


A PRACTICAL COURSE OF MILITARY SURVEYING. 


carry with him in the field, or even construct himself in an emergency. 
We shall successively learn the use of the prismatic compass and the 
plane-table; and when they are thoroughly understood we shall readily 
employ any other, since the problems of topography are but few. 
Simplicity is the first condition which the instruments of a soldier should 
fulfil: theodolites, circumferentors, &c., are no doubt most valuable in¬ 
struments in the hands of the engineer who surveys at leisure in time of 
peace, but for the field they are most decidedly unfit ; the more numerous 
the adjustments, screws, .glasses, &c., the more numerous the causes of 
error, and also the more subject the instrument is to be put out of order. 
However, as the box-sextant and the cross-staff are very portable, we shall 
conclude what we have to say on the measurement of angles by a few 
words on those two instruments. 


CHAPTER Y. 


PRISMATIC COMPASS. 

(71.) The prismatic compass is founded upon the property of the 
magnetic needle to constantly point to the magnetic pole, when 
horizontally supported on a pivot so as to turn freely. 

The angle formed by a line and the magnetic meridian is called the 
magnetic azimuth of that line, and the value of this angle is called a 
hearing. 

The prismatic compass is employed to take bearings, and therefore 
to measure the angle formed by two directions, since their angle is equal 


Tig. 63. . 



to the difference of their azimuths. The angle B A C, for instance, is 
equal to azimuth B A 1ST—azimuth CAN. 

(72.) In its most general form this instrument consists of a compass 
card C (Fig. 64), divided into half degrees from 0° to 360°, and fixed on 
a magnetic needle, which is supported on an agate centre, round which it 
turns freely. A sight-vane, S, is provided with a thread stretched along its 
opening; and a narrow slit, cut through the prism P, serves as the eye¬ 
sight. Both the sight-vane and the prism are mounted on a hinge- 

E 




50 


A PRACTICAL COURSE OF MILITARY SURVEYING. 


joint, so as to be turned down flat, to permit putting the instrument in 
a case when not in use. 

Fig. 64. 



The prism can be raised or lowered in a socket, to facilitate the 
reading of the graduations of the card as they pass in succession 
before it. 

A little spring, usually under the sight-vane, serves to check the 
vibrations of the card, when taking bearings. 

To take the bearing of a direction A B, station at A, turn the prism 
and sight-vane up, as in the last diagram, raising or lowering the prism 
until the divisions of the card become distinctly visible, and hold the 
instrument horizontal, either in the hand or on a stand. Turn it round 
until the object B is seen through the slit in coincidence with the thread 
of the vane; check then the vibrations of the card by pressing on the 
spring, and the graduation of the limb that is seen to correspond to the 
thread gives the required bearing or magnetic azimuth of line A B. 

Bark glasses are sometimes added to the prism to take azimuths of 
the sun, and a mirror is also found sliding along the sight-vane to reflect 
the image of objects much above or below the level of the eye; but they 
are useless for military purposes. 

(73.) The angles measured with the prismatic compass are obtained 
reduced to the horizon, and this advantage, together with the portability 
and simplicity of the machine, renders it essentially fit for officers in the 
field. It is almost exclusively employed to fill in the details of extensive 
surveys, and also to make the triangulation of military sketches. 

(74.) In order to protract the bearings several parallel lines are 
previously drawn across the minute, more or less close, according as the 
details are more or less numerous. They represent the directions of the 
magnetic meridians, which can be considered sensibly parallel in ordinary 







PRISMATIC COMPASS. 


51 


surveys. An advantageous contrivance consists in drawing them at 
intervals equal to the divisions of the scale employed. Thus at the 
scale of 4 inches to a mile, if we make those intervals alternately equal 
to the i and the i of an inch, they will represent 110 and 55 yards, and 
serve in filling in the details. 

(75.) The protractor consists of a semicircle of thin transparent 
horn. Its circumference is subdivided into degrees and half degrees, 
and its graduations on the outer arc extend from right to left from 
0° to 180°, whilst on the inner arc, corresponding to the rest of the cir- 

Fig. 65. 



cumference, the graduations from right to left run from 180° to 360°. 
The margin A B is parallel to the diameter 0—180. 

There is another kind of protractor, formed of a rectangular piece of 

Fig. 66. 



ivory, divided and graduated from left to right, as in this diagram, the 
margin A B coinciding with the diameter 0—180. Its surface* is 
covered with a series of parallel lines perpendicular to the margin. 

e 2 




















































52 


A PRACTICAL COURSE OF MILITARY SURVEYING. 


In protracting the bearings it should be carefully borne in mind 
that they are counted from north to east, south and west. 

If we want, for instance, to protract a bearing of 50° taken at C, 
place radius 50° of the horn protractor on one of the parallel lines, and 
slide it along until the margin passes through C, then draw C B. 

Fig. 67. 



From 0 to 180°, the graduations of the outer circle serve to protract, 
but from 180° to 860° we have recourse to the inner circle. 

When employing an ivory rectangular protractor, these parallel lines 
will represent perpendiculars to the magnetic meridian, and correspond 
to those that are drawn across the instrument. To protract with it a 

Fig. 68. 





















PRISMATIC COMPASS. 


53 


bearing of 60°, for instance, through c, place the centre of the pro¬ 
tractor at c, and make any one of the lines across it coincide with one 
of those drawn on the paper, without moving the centre from c. The 



Fig. 69. 

cN 


X 


X 

/ 


— - 

X 

~2 



z 


IX 






w 


-- C 


E 







== 










margin A B coincides then with the magnetic meridian. At the 
extremity of radius 60° make a dot with the pencil, and the line drawn 
from c to that dot will bear 60° with the magnetic meridian. If 
the bearing is greater than 180°, the protractor is placed to the 
left of the point c, and the graduation of the inner circle serves to pro¬ 
tract the angle as before. 

Although the ivory protractor is most generally employed in this 
country, preference should be given to the horn one, as giving more 
exactitude : it will, in fact, be readily understood that the slightest de¬ 
viation from coincidence between the short line across the ivory instru- 


Fig. 70. 



ment and that of the plan, will, owing to that shortness, much affect the 
true position of the margin. The same deviation with the horn instru¬ 
ment, whose radii are all equal, will not produce so great an inexactitude. 























54 A PRACTICAL COURSE OF MILITARY SURVEYING. 

The following problems will familiarize with the use of the 
prismatic compass :— 

(76.) 1st. To find the projection of a point, X, knowing those , a, b, of 
two given points , A and B. 


Fig. 71. 
X 



Station at A, take the bearing of A X; repair to B, take the bearing 
of BX; protract those angles through a and b, the projection x is 
found. 

This problem enables us to fix on the plan the station we occupy on 
the ground we survey. 

If A and B are inaccessible and X accessible, station at this point, 
take the bearings of X A and X B, protract them through a and b as 
before, and produce a x and b x till they meet in x. 

This method of intersection is very expeditious, since several 
azimuths can be obtained at the same station (Fig. 72). The angles 


Fig. 72 . 



z, y, x, &c., should not be too acute (44), and when we find them to 
be so, we must verify the position of those points by taking a third 
bearing from another station, from c, for instance. 

































PRISMATIC COMPASS. 


55 


(77.) 2nd. To survey a road A B C D. 

Station at A, take the bearing of B, protract it through a: measure 
A B and carry it on a b at the scale. At B take the bearing of C and 
protract it (Fig. 73), measure B C, draw it on b c, and so on. This 
method, known under the name of traversing, can be simplified by 
omitting every other station, B, D, &c. Having taken and protracted 
the bearing of B, we measure A B, and without stationing at B we go 

Fig. 73. Pig. 74 




on and measure B C. Arrived at C, we mark the distance a b at the 
scale, and take the bearings C B and C D, which we protract, and 
having carried distance B C on b c, we start afresh. This expeditious 
process is called taking the back angle. 

If some points of importance, H, M, N (Fig. 74), lie on either 
side of the road, their bearings, taken from A, B, 0, D, enable us to 
determine their projections on the plan. 

3rd. To trace the direction of the capital of a bastion or of an in* 
accessible worlc, (Fig. 75.) 

Mark two points, a, b, on the direction of the prolongation of the 




































































56 


A PRACTICAL COURSE OF MILITARY SURVEYING. 


faces; take the azimuth a of a A, that /3 of b B, and their difference 

a —/3=angle A C B, and the angle formed by the capital and 

either face. 

Fig. 75. 



(78.) This instrument is preferable to the plane table in moun¬ 
tainous or woody countries where several points cannot be seen from a 
same station. It is the best instrument for military purposes. 

In using the instrument, it is advisable to place it on a stand, 
because while holding it in the hand the slightest motion of the body 
precludes accurate reading, and also because it becomes easier to place 
the sight vertical, a most important condition, inasmuch as its obliquity 
may cause errors of even 10 degrees in the azimuth of an object much 
above the horizon. We should also carefully avoid the vicinity of any 
steel scabbard, sword, bayonet, and even carry no knife or key in our 
pocket, for they would affect the direction of the needle. 

(79.) The magnetic and terrestrial meridians do not coincide; the 
angle they form at a given point is called the declination or variation. 
It can be found by tracing a terrestrian meridian and comparing its 
direction with that of the needle. Conversedly, by means of the decli¬ 
nation, the true meridian can be obtained. 

This declination varies in different parts of the globe; but a pris¬ 
matic compass constructed for England may be employed anywhere, 
since the angles it determines, being the difference of two azimuths, are 






PRISMATIC COMPASS. 


57 


not altered where both bearings are simultaneously larger or less by the 
same quantity. The survey will therefore proceed equally well; but we 
shall require the declination to trace the direction of the true meridian. 

The variation, for the same locality, is subject to periodical changes; 
thus, in 1580, it was 11° 30' east at Paris; it was 0 in 1603, and 19° 26' 
west in 1861. Besides those local and periodical changes in the decli¬ 
nation, the needle presents diurnal variations which may amount to as 
much as 25 minutes: they will of course affect more or less the exacti¬ 
tude of the survey ; but as the prismatic compass serves only to fill in the 
details in regular surveys, the error can be neglected. 

(80.) A French officer, M. Trinquier, has lately invented an instru¬ 
ment, eclielle-rapporteur, which is admirably suited for field purposes, 
inasmuch as it permits to protract bearings and lay down distances 
without protractor rule, scale, or compasses. The principle is so simple 
that one may be constructed in a few minutes. It consists of a board, 

Fig. 76. 



A B C D, on the middle of which is fixed a circle of thin pasteboard 
movable in every direction round its centre, E. Its circumference is 
divided into 360°, and its surface is ruled over by two systems of 
parallel lines at right angles to one another. 

The lines parallel to diameter 90°—270° are red, and are at inter¬ 
vals more or less great, according to the scale of the intended sketch, 
each interval representing 10, 20, &c. paces. Every fifth line is made 
















58 


A PRACTICAL COURSE OF MILITARY SURVEYING. 


thicker to facilitate the reading. The other set of parallels is black, 
and the lines are at any interval deemed convenient. 

An index is invariably fixed on the board at G-; it touches the 
graduated circle, but does not prevent it from turning. The diameter 
Gr E will represent the magnetic meridian. 

The paper on which the sketch is to be made must be thin or 
transparent; it is stretched over the board, and is kept in its place by 
four drawing-pins, p, p, p, p. The board is cut out on one side to 
allow the fingers to turn the circle. 

To trace a direction, the bearing of which is found to be, say 130°, 
we turn the circle until graduation 130° comes under the index Gr: it 
is clear that all the black lines are now parallel to the direction required, 
and this is at once traced by following with a pencil the black line seen 
through the paper. The distance measured in that direction—say 150 
paces, is laid down by marking over the black line across 15 intervals 
of the red lines. 

The instrument may be made still more handy in fixing the pris¬ 
matic compass in a corner of the board by means of two brass screws. 


59 


CHAPTER VI. 

PLANE TABLE. 

(81.) The 'plane table is employed to draw the angles at the same 
time they are observed, instead of measuring them and protracting 
them afterwards. 

In its most complete state it consists of a square hoard of wood 
about a foot or eighteen inches square, mounted on a tripod stand; it 
can move freely on that tripod, and be placed in any position in which 
a clamp screw permits to fix it. The paper is stretched and fixed 


Fig. 77. 



upon this board. The angles are observed by means of a brass rule 
supporting a telescope movable in a vertical plane round the point of 
support. * 

This instrument was hitherto much complicated by a quantity of 









60 


A PRACTICAL COURSE OF MILITARY SURVEYING. 


contrivances destined to render it more perfect, bnt in reality adding 
to tlie causes of error; it is at present very seldom employed in tins 
country by civil engineers, or officers. For military purposes, however, 
it is unquestionably a most valuable instrument, which saves both time 
and trouble; and its construction can be so simplified as to enable 
almost everyone to attempt it. 

The staff officer in France frequently carries his plane table in his 
holsters: it is formed of 6 thin rules, about 2 inches wide and 1 foot 
long, pasted on a piece of linen or kid, on which the paper is fixed. 
These rules are parallel and a little apart, so as to be easily folded flat 
together. Two other rules, A and B, maintain them open and give 


Fig. 78. 



strength to the whole; they turn on a pivot at one end, and a hook at 
their other extremity catches a ring screwed to the splits 1 and 6. A 
movable socket under the rules 3 and 4 permits to fix this table on a 
stick when it is required for use. After work, the stick is removed, 
the socket unscrewed, the hooks unfastened, the rules A and B turned 
round their pivot till they coincide with splits 1 and 6, and the various 
pieces folded alternately one upon another. (See 90.) 

The telescope, or sight ruler, is replaced by a wooden ruler with 
two needles fixed in an upright position. 

Fig. 79. 


A plane table may also be formed with a piece of pasteboard pro¬ 
vided with a socket of strong paper, into which a stick may be inserted 
fot support. The sight, reduced to its most simple form, will be the 
edge of a piece of paper folded longitudinally. 















PLANE TABLE. 


61 


The sketch book on the left arm might even be a substitute for 
the table. 


Pig. 80. 



(82.) Whatever the form of a plane table may he, we use it for 
fixing on the minute the projection of the vertex of a triangle, a side 
of which is given, or two vertices of a quadrilateral figure knowing 
the other two, or the fourth vertex knowing the other three. In all 
these problems, the angles are traced instead of being measured. 

(83.) 1st. To fix on the plan the projection of a point , X, having 
already those , a, b, of two accessible points , A and B. 

Station at A placing the table as level as possible by moving its 

Pig. 81. 


X 



legs ;• place the sight ruler on ab, and turn the table till the point B is 
seen in a line with the edge of the ruler; then the line a b has been 
placed in a same vertical plane with A B, and the table is clamped firm 












62 


A practical course of military surveying. 


in that position. Keeping* the edge of the ruler on the point a, turn 
it till it is* in a line with X and draw a x. 

Repair to station B and repeat the same operations : place the ruler 
along a b, turn the table till A be in a line with it ; clamp the screw, 
turn the ruler round b till x be in a line with it, and draw b x. 

The intersection of a x and b x determines the projection x of the 
point' X and the angles B A X, A B X have been traced and at once 
reduced to the horizon. 

In an open country several points, x, y, z, t, may thus be determined 
by one station only at each extremity of the given line, A B. (Fig. 82.) 

Fig. 82. 



(84.) 2nd. One of the tivo given points, B, is inaccessible. 












PLANE TABLE. 


63 


Station at A, and draw a x as above. Station at X, place the ruler 
along a x, turn the table and clamp it as soon as A is in line ; place 
the ruler’s edge on b, and turn it round till B is seen, trace a b, which 
intersects a x, at the required point x. 

(85.) 3rd. The tioo given points are inaccessible, but a station can be 
made between them . 

Station at a point C situated on direction A B, and on the plan 


Fig. 84. 



(Fig. 84) mark in c / its supposed projection. Place the ruler on a b, 
and turn the table till A (or B) be in line, and clamp it. Place the 
ruler on c / and make it move round it till X be in line, and draw c,X/ 
giving angle x / c / b=X C B ; plant a staff or leave a man on C. 

Bepair to X, place the ruler on x,c, turn the table till C be in line, 
and clamp it; put the ruler on b and move it round till B is in line, 
and draw b x; put the ruler on a and turn it till A is in line, draw a 
x, which intersects b x at the required point. 

(86.) 4th. To fix the projections of two accessible points, X and Z ’ by 
means of two inaccessible given points, A a, B b. (Fig. 85.) 

On a corner of the minute, or on a piece of paper provisionally 
stuck on it, draw a line x,z, which we suppose to represent X Z. 
Station at X, and place x,z, in the same vertical plan with X Z (84), 
and clamp the table : put the ruler on X, and turn it till A is seen in 
line, and draw x,a,; turn again till B is in line, and draw x,b,. Bepair 
to Z, and by a similar operation draw x,a /} zJj,. 

A quadrilateral figure, XyZ^b, is thus formed, similar to A B X Z. 




64 


A PRACTICAL COURSE OF MILITARY SURVEYING. 


To fix it at the scale on the minute, on a y b,> take b / o=a b, and 
draw o p parallel to a,z /5 r and o q parallel to z,x ,; the figure b, o p q 
represents] the quadrilateral figure A B X Z at the scale. It is then 
easy to draw it on a b: from a as centre with radii o p, o q describe two 


Fig. 85. 






circumferences ; from b as centre with radii b,p, b,q, describe two other 
circumferences, which shall meet the former in x and z, the required 
projections. 

To draw through a given point a line parallel to a given line, place 
the sight ruler on the line and look for some object 200 or 300 yards 
distant in that direction: move the ruler to the given point and turn it 
round till the same object be in line the edge of the rule will be paral¬ 
lel, or very nearly so, to the given line. 

The parallels o p, o q, are usually drawn in that manner. 

5th. Three inaccessible points, A, B, C {a, b, c), being given, to 
determine the projection of a fourth point, X, accessible. 

The point X is at the same time on the segment of circle described 
on A B and containing the angle A X B, and on the segment contain¬ 
ing angle B X C described on B C. If, therefore, we station at (Fig. 
86) X, and construct the angles A X B and B X G, which is easily 
done by assuming any point, x, for vertex on an auxiliary piece of paper, 
and aiming with the ruler successively at a, b, and c, and tracing X A, 








PLANE TABLE. 


65 


Xjbj, XjC,, the projection X will be determined on the plan by describing 

Fig. 86. 



on a b a segment that contains angle a, x, b„ and on b c a segment 
containing angle bj x t c r 

This process is not very practical. Among several other methods 
the best consists in fixing on a corner of the table a piece of tracing- 
paper. Taking on it any point, x, at random we draw as above the 
lines Xj a^ x t b 1? x 1 c v making the angles A X B, B X C. 

Unfastening the tracing-paper, we move it on the minute till these 
three lines pass respectively through a, b, c, and then we prick x, and 
obtain the required projection. 

This problem enables us to find our place, x, in a survey by means of 
three given points. 

The plane table is an excellent instrument in even and open ground, 
where a canvas is rapidly constructed; and those officers who have 
once employed it will always prefer it to any other; nevertheless, it 
should be rejected in mountainous or woody countries, where several 
points can seldom be seen from the same station. 

(89.) A magnetic needle or compass may be advantageously added 
to the plane table for the purpose of facilitating the finding of a station. 
"When the projection a b of a line, A B, has been placed in the same 
vertical plane with A B (84), read the angle marked by the needle, and 
whenever it is required to place the table in a position parallel to this, 
it is done by turning it till the compass gives the same reading. 

By means of this addition the plane table permits to operate with 





66 


A PRACTICAL COURSE OP MILITARY SURVEYING. 


great rapidity. Let us suppose, for instance, that in the course of a 
survey it is required to fix the projection of an accessible point, X, 

Fig. 87. 



knowing those, a, b, of two points, A, B, in other words, to find our place 
in a survey (76), having already fixed a, b, on the minute. Stationing 
at x, turn the table till the compass gives the reading alluded to: 
clamp the table, place the ruler on a, and turn it till A is seen ; draw 
a x: place then the ruler on b, turn it until B is seen, and tracing b x 
it will intersect a x at the point x of station. If a compass cannot be 
procured, we may fix a pin or a needle on the plane table, and with the 
help of a watch construct its shadow during the different hours of the 
day. The sun-dial resulting therefrom will serve for the few following 
days; and to place the table in a direction parallel to that of departure, 
it will be sufficient to turn it until the shadow corresponds to the hour 
at which we require this parallelism. 


Fig. 88. 



(90.) A plane table was lately constructed by Major Fevre, of the 


















PLANE TABLE. 


67 


French Staff-Corps, for military reconnaissance. It is 11 inches long, 
8 inches wide, and weighs only 28 ounces. The sides are surrounded 
by a brass tube, A, destined to receive a bolt, B, which carries with itself 
all round the table both the magnetic compass and the sight ruler. 
This bolt is introduced into the tube by means of a slit, C, closed by a 
spring, and a screw, D, permits to clamp the ruler and compass when¬ 
ever necessary. The sight ruler is made of wood, and when not in use 
its brass pins can be buried in grooves cut through it. Under the 
table we find a hollow handle of wood, E, movable round a spherical 
joint, F, so that the table may be held in the left hand whilst on horse¬ 
back, or fixed to a stick when on foot. 


Fig. 89. 



The paper is fixed to the table by means of four grapples, and 
rendered tight by screws protruding underneath. 

When the instrument is not in use, the sight ruler, the magnetic 
compass, and a plummet of wood can be placed in hollows, scooped out 
in the under surface of the table, and the whole may be carried by a 
string attached to the handle. 

The magnetic compass is of a peculiar description; the bottom of 
the box is movable and bears two diameters at right angles, each letter, 
N, S, W, E, corresponding to a side of the table. When at the 
beginning of a survey the azimuth of a direction is taken, the extremity, 

f 2 














68 


A PRACTICAL C0U11SE OF MILITARY SURVEYING. 


S, for instance, is brought under the point of the needle. The compass 
being afterwards moved to one of the adjacent sides of the table, the 
needle will point to W, N, or E, as the case may be, thereby avoiding 
the necessity of adding 90° to the azimuth whenever the compass 
changes side. 

Fig. 90. 



(91.) Major Fevre combines the scale and compasses into one instru¬ 
ment. It consists of two rules of equal length, the wider one carrying any 

Fig. 91. 

s s' 


11114 -u - i m 


o 





A 


s 


i i \ j ruijTrm n ii in i ii m~~ 

• 

a- l 

• 


1 i'y'rr i iriii T--T-f= 

• 


• 



two scales, say four inches and two inches to the mile. These two rules 
can slide upon one another, so that at both extremities the distances, a b, 
are equal. Two steel points, s s, fixed at the end of each ruler, will thus 
enable us to measure or carry a distance, the reading of which is found 
at the extremity, E, of the small rule. A scale of paces may also be 
made on the bottom of the groove of the wider rule. 

This plane table working excellently in the field, is now superseding 
all others. 




























69 


CHAPTER VII. 

SEXTANT AND CROSS-STAFF. 

(92.) The box sextant is employed to measure the angle between 
two objects. It consists of a cylindrical box containing an index- 
mirror, under A, to which is attached on the upper surface or plane of 
the sextant an index-arm, E. Both this mirror and the index are 
movable by means of a screw, B. The index-arm is terminated by a 
vernier wherewith we read the graduations of the limb, m n, within a 
minute (95). The graduation extends from 0° to 120°; and a magni- 
fying glass, M, facilitates the reading. 

The sight D, to which a telescope may be adjusted if required, is 
opposite to another mirror (under Gr), called the horizon-glass, that has 
half its surface silvered. 

Both mirrors are fixed, by the maker, perpendicularly to the 


Fig. 92. 



plane of the sextant. By means of two levers in H the observer 
interposes two dark glasses between the mirrors and an object too 
brilliant to be easily seen, and the eye-piece of the telescope is also 













70 


A PRACTICAL COURSE OE MILITARY SURVEYING. 


provided with a dark glass for the same purpose. It is often recom¬ 
mended to adjust this instrument before employing it, but we should 
advise officers to meddle as little as possible with adjustments: if the 
sextant is put out of order, it is better to send it to the optician; yet, 
as accidents will happen in the field, and opticians are not always at 
hand, here is an account of the process. 

(93.) To be in perfect adjustment, both the index-mirror and the 
horizon-glass should be perpendicular to the plane of the sextant, and 
both parallel when the vernier is at 0. 

Through the process of construction of the maker, the index-mirror 
is supposed to be right, therefore we have only to ascertain the per¬ 
pendicularity of the horizon-glass. To do so, hold the sextant 
horizontally and look through the sight D, at the distant horizon or 
at the sun. If two images appear, unscrew the key C, and putting it 
to the key-hole G, turn it till the two horizons or the two suns coincide. 
The glass is then right. 

To verify the parallelism, place the index exactly at 0, and, holding 
the instrument horizontal, look to the angle of a house far distant or to 
the lower limb of the sun—so placing the eye as to see directly through 
the hole of the slide and the unsilvered part of the horizon-glass. The 
direct image and that reflected by the index-mirror to the horizon-glass 
should appear as one: if not, fit the key 0 to the key-hole I, and turn 
till both images coincide. The instrument is then adjusted. 

(94.) To measure the angle between two objects, set the vernier at 
0°, hold the instrument with the left hand in the plane of the objects, 
look through the slide D or the telescope at the left-hand object, and 
with the right hand turn the screw A until the reflected image of the 
right-hand object coincides with the direct image of the left. The 
vernier marks then the angle required. 

To obtain the angle subtended by two objects situated in the same 
Vertical plane, set the vernier at 0, hold the instrument vertically in 
the right hand, and bring the reflected image of the upper object to 
coincidence with the direct image of the lower one. The vernier marks 
then the required angle. 

(95.) The vernier is a contrivance applied to an instrument employed 
for the measurement of angles or distances, so that the fraction of the 




SEXTANT AND CROSS-STAFF. 


71 


smallest division of a graduated limb or scale may be read. It consists 
of a little arc or rule according as tlie graduated scale is a circumference 
or a straight line. 


Fig. 93. 



f , f 

“ i f i f 



. Mill 1 1, 1 1 1 

nTTlTTTTlTTTTtTTTT 



TjTj 1 | 1 | 1 

TT ] ITI 1 |l 1 1 i 1 

i'[ [ r i | 1 1 1 1 1 1 1 | 1 n\ 



1 1 1 1 1 1 1 IT 

TT 1 t ! !TT\ 



l l 

l 30 

^ I ^ 


Let us take on the limb and on the vernier two equal lengths or 
arcs, the first containing n—1 divisions equal to D, the second n 
divisions equal to d. These lengths will therefore be represented by 
(n—1) D and n d, and as they are equal (n—1), D=n d, hence 

D — d=^ It follows from this that when the 0 of the vernier has 
n 

passed a division of the limb, this 0 is in advance upon it of 

]) op 3D 

—* -•’ -- &c., according as the first, second, third, &c., of its own 

n n n ° 

divisions coincides with one of the limb’s divisions. Hence, when 
measuring distances or angles with an instrument provided with a 
vernier, we must ascertain which division of the vernier coincides, 


multiply it by and add this product to the last division of the limb 

over which the 0 of the vernier has passed. In the box sextant the 
value of D=30 minutes, and n=30, therefore D—d=T. The limb is 
divided in half-degrees, and 30 divisions of the vernier correspond to 29 
of the limb. If the 0 of the vernier (marked with an arrow) has passed 
the 12th degree of the limb, for instance, and if its 9th division 
coincides, the angle measured is 12°—9'. If the arrow has passed 
43° 30' and the 23rd division of the vernier coincides, the angle 
=43° 53'. 


(96.) The box sextant seems preferable to the compass when accuracy 
of measure is requisite, since it can, even without employing a stand, 
give an angle accurately within one minute, and measure the angles of 
elevation and depression besides. It has, however, the drawback of 













72 


A PRACTICAL COURSE OF MILITARY SURVEYING. 


furnishing us with the actual angle instead of its horizontal projection, 
and a complete series of angles round a station may considerably exceed 
or fall short of 360°. The error due to this cause exceeds that of the 
prismatic compass used with a stand, and the exactitude of measure¬ 
ment is, after all, hut apparent, therefore the sextant cannot he 
preferred to the compass. 

There is a mode of reducing angles to the horizon, hut it is tedious* 
and should he avoided: a little practice will enable the observer to do 
it himself by selecting a point exactly vertical above or below the 
objects, in the plane of the true horizon. 

(97.) In order to understand upon what principle the sextant is 
constructed, let it be observed that if a ray of light, 0 R, falls obliquely 
upon a mirror, A B, it is reflected in a direction, R I, making with 


Fig. 94. 
'V 



the perpendicular, Y R, the angle of reflection, I R Y, equal to 
the angle of incidence, 0 R V. How, when two mirrors, A B, AC, 
form between themselves an angle, a , if a ray of light, 0 R, falls 

Fig. 95. 



upon one of them, AC, to be reflected to the other, A B, hi 
R R', and there again reflected in the direction R' I, the angle 
formed by the direct ray, 0 I, and its reflected image, R' I, is double 
the angle «. This is seen at once on the figure : Angle R'IO=RR'I 





SEXTANT AND CROSS-STAFF. 73 

+ E' E 1=180 — 2 / + 180 —2 r=360—2 {r+r'). But in triangle 
A E E', a=180 — (r + r), therefore E' I 0=2 a. 


Fig. 90. 



Let A he a mirror (Big. 97), B another one with half its surface sil¬ 
vered, and M P two objects subtending an angle, M E P. The image 
of M is reflected from A to B, and from B to E, and the angle 


Fig. 97. 



A E B is, according to what has just been said, equal to twice the 
angle o A Gr of the mirrors. Now, if P is in a line with E B, the 
angle A E B is precisely the angle required. 

In the box sextant the mirror A constitutes the index-mirror, and 
B the horizon-glass. As the latter is unsilvered in b b, the object P is 
perceived directly along E P; therefore, if the mirror A is turned 
until the reflected image of M coincides with P, the two mirrors will 
then make an angle equal to half that subtended by the objects. In 
the box sextant, the index-arm A Gr, fixed to mirror A, points to the 
graduation of the limb L 0, which is numbered double, so as to give 





74 


A PRACTICAL COURSE OF MILITARY SURVEYING. 


the real angle at once. When the movable mirror, A, is parallel to B, 
the index points to o. 

(98.) The problems which we have investigated with the plane 
table and the prismatic compass can be solved by means-of the sextant, 
by measuring and protracting the angles instead of tracing them, as 
with the table, and plotting them by differences of azimuths, as with a 
compass. We shall not, therefore, repeat their solution, as the student, 
having once understood how to handle the sextant, can easily find it. 
One application or two, however, may be given. 

1st. Through a given point , A, to trace on the ground a line perpen¬ 
dicular to a given line , B C. 

If A is without B 0, plant a staff at it, set the vernier at 90°, 
and marching from C to B, look through the slide towards B till 

Fig. 98. 


the reflected image of the staff coincides with B. The point D, at 
which the coincidence takes place, determines A D, at right angles 
with B C. If A is on B C, set the vernier at 90°, and send a man 
with a staff to the right, while you stand at A and look through the 


Fig. 99. 

}A. 

^ 


slide at C (Fig. 99). As soon as the reflected image of the man coincides 
with C stop him, and the point D, which he then occupies, determines 
A D perpendicular to B C. When the man is sent on the left the 
sextant must be inverted. 






SEXTANT AND CROSS-STAFF. 


75 


2nd. To find the distance between A accessible and C inaccessible. 

Fig. 100. 



Set the vernier at 90°, and through A trace a perpendicular, AB to 
C A, as explained; then set the vernier at 45°, and marching in direction 
B A, and aiming at A, move backwards or forwards until the re¬ 
flected image of C coincides with A. The point B, at which it 
happens, gives us the isosceles triangle CAB, and B A=A C. 


(99.) By means of the cross-staff, an instrument very familiar to 
Civil surveyors, perpendiculars on the ground are traced; it can 
advantageously he employed in military surveys to fill in the details. 

It has various forms. The most general consist of a cylinder or a 


Figs. 101 and 102 




prism of brass, having four longitudinal grooves, cut through so as to 
give two directions, at right angles. 
















76 


A PRACTICAL COURSE OF MILITARY SURVEYING. 


It is sometimes formed of a circle of brass with two diameters at 
right angles bearing a sight at -each extremity. 


Fig. 103. 



In whatever form, it is fixed upon a stand so pointed at its 
extremity as to be easily driven and steadied into the ground. 

As it very seldom happens that this instrument is to be found in 
the field, it can easily be replaced by a small board nailed to a stick. 
Four needles or pins planted at right angles, as in the diagram, will 


Fig. 104. 



answer the same purpose as the grooves. This instrument will be 
found very handy in mountainous and woody districts, ravines and 
marshes; and when measures are taken by pacing, the details of a survey 
may be rapidly filled in by its assistance, as may be seen by the follow¬ 
ing few exercises. 

(100.) 1st. Through a given point , A, to trace a perpendicular to a 
given line , B C. 

Fig. 105. 

I A. 

_ _c 

p ' ; 

March along B C, carrying the instrument with the left hand, and 
aiming along that direction through a groove, and see through the 
other if you can perceive the point A, if not, march on. After a few 
trials the point A will be seen ; then the point P, from which A is seen 
through the second groove, gives the extremity of the perpendicular 
required. 






SEXTANT AND CROSS-STAFF. 


77 


(101.) 2nd. To produce a line beyond an obstacle. 

Let A B be the line \ at B trace B C, perpendicular to A B, which 


Fig. 106. 



cl-l D 


is done by looking through a groove along B A, and sending a marker 
to plant a pole in the exact direction of the rectangular groove ; 
measure B C, trace C D perpendicular to B C, and produce it till the 
obstacle is passed; trace D E perpendicular to D C, making it equal to 
C B ; then E E traced at right angle with E D will be in the pro¬ 
longation of A B. 

(102.) 3rd. Through a given point, A, to draw a line parallel to a given 
line, B C. 

Fig. 107. 

S_T> 


X Tr 

Eind on C B the foot of the perpendicular A D. Place the cross- 
staff in A, one sight directed on A D, the other will be directed on A H 
parallel to B C. 

(103.) 4th. To find the distance between two points, A, B, one of 
which, A, is inaccessible. 

Fig. 108. 



In B trace a line, B C, perpendicular to B A, and mark its middle, 
D; at C trace C E at right angle with C B, and march along it till 












78 


A PRACTICAL COURSE OF MILITARY SURVEYING. 


arrived in E yon perceive D and A in a line, the length C E measures 
then A B. 




G 



ii 


Trace any direction, C D, and mark on it the extremities C and D 
of the perpendiculars A 0, B D, respectively drawn from A and B to 
that line; produce them on C G, D H. Bisect CD in E. March 
along D H till you see E and A in the same direction, and mark the 
point H from which you perceive the coincidence. 

Do the same operation on C Gr, till in Gr you see E and B 
coinciding in direction. The line G H measures A B. 

(105.) 6th. To survey a polygon, ABODE. 

Trace the diagonal A B: find in it the feet of the perpendiculars 


Fig. 110. 


] 



a 


c 


p C, p' E, p" D. Measuring the distances A p, p p', p' p", p" B, and 
the perpendiculars p C, p' E, p" D, the figure can at once he drawn. 






SEXTANT AND CROSS-STAFF. 


79 


The sinuosities of a river, a wood, a piece of water, &c., can be 
obtained with great exactitude by this process:—Advancing along a 


Fig. 111. 



line, A B, measuring successively the distances A m, m m', &c., and 
their perpendicular offsets, An, mm, m'n, &c. 

(106.) The area of a field can also be found with the help of a 
cross-staff. To do this, trace a rectangle, A B C D, that encloses the 


Fig. 112. 



field. Draw it at the scale on a piece of thick paper; march along 
the sides of the rectangle, taking the offsets as before described, and 
draw the borders of the field. Calculate the area of the rectangle: cut 
it and weigh it: cut out the field and weigh it. Its area has to that 
of the rectangle the same proportion as is given by the weights. 












80 


A PRACTICAL COURSE OF MILITARY SURVEYING. 


CHAPTER VIII. 

LEVELLING. 

(107.) To level is to find the difference of level between two or more 
points. Let A and B represent two points fixed on the plan by one of 
the foregoing methods. In the triangle ABH, the angle H is right, 

Fig. 113. 



the projection A H is known by measuring it at the scale; therefore, 
if we could observe the angle of elevation B A H, we could obtain the 
altitude B H by either calculating or constructing the triangle ABH. 

Again, if H B was directly or indirectly measured the problem 
would be solved. 

The instruments of levelling are of two kinds: some give us the 
angle of elevation or of depression, others the height itself. 

The only instruments that can be recommended to an officer for the 
purpose of observing these angles, are the box sextant already described, 
and the clinometer. 

(108.) The clinometer consists of a quadrant of pasteboard or of 
Fig. 114. 



brass, having a plummet, A H, suspended at its centre, and graduated 
as in the diagram on both sides. When we require an angle of eleva- 






LEVELLING. 


81 


tion ABH, we look along the edge A C, till B be in sight, when the 
plummet indicates the angle 0 C Y. For an angle of depression 
reverse the instrument. 


Fig. 115. 



The clinometer is quite sufficient for every military purpose, and its: 
extreme simplicity renders it preferable to the box sextant. At all 
events it makes a capital substitute for it in case of accident. 

(109.) If a sextant is used (94) in the mode described, the angle 
A H B which it gives will not differ much from the true angle of 


Fig. 116. 



elevation A O B when the distance H B is great, and if the operator 
lies or stoops on the ground this angle will be sufficiently exact. 

Fig. 117. 



Where a great accuracy is necessary, a reflecting surface should be 
procured to give a horizontal plane. A hollow vessel, filled with a few 
inches of water or mercury, will at once procure this artificial horizon; 








82 A PRACTICAL COURSE OP MILITARY SURVEYING. 

a looking-glass might also he placed level. Whatever he this auxiliary 
surface, we measure with the sextant the angle BOB' formed by an 
object B, and its reflected image C seen on direction B'. This angle is 
double the elevation required, since MOB=OON (97), and C 0 N= 
MOB'. 

(110.) The distance A B and the angle B A C being known, the 
height B C can be found by the formula H=B tang a, in which B 


Pig. 118. 



represents the horizontal distance, a the angle of elevation and H the 
altitude. 

Table showing the Height when the Horizontal 
distance A B=100. 


Angle. 

Height. 

Angle. 

Height. 

Angle. 

Height. 

1° 

T74 

16° 

28*67 

31° 

60-07 

2 

3-49 

17 

30-57 

32 

62-49 

3 

5-24 

18 

32-49 

33 

64-94 

4 

6-99 

19 

34-43 

34 

67-45 

5 

8-75 

20 

36-40 

35 

70-02 

6 

10-51 

21 

38-39 

36 

72 65 

7 

12-28 

22 

40-40 

37 

75-35 

8 

14-05 

23 , 

42*45 

38 

78T2 

9 

15-84 

24 

44-52 

39 

80-98 

10 

1763 

25 

46-63 

40 

83-91 

11 

19-44 

26 

48-77 

41 

86-93 

12 

21-26 

27 

50-95 

42 

90-04 

13 

23-09 

28 

5317 

43 

93-25 

14 

24-93 

29 

55-43 

44 

96-57 

15 

26-79 

30 

57-73 

45 

100 


An example will show how to use this table. The distance be¬ 
tween two points is 457 yards—the angle of elevation 10°. 

In the column of angles we find that for 10° there is a difference 
of level of 17'63, when the base is 100 yards ; therefore, 100 : 457 :: 
17*63 : to the height required=80'55 yards. 











LEVELLING. 


83 


If the student is not acquainted with Trigonometry, or if there is 
no table of tangents to be had, a scale of height may be constructed in 
the following manner:—0 H representing the horizon, draw through 
0 several lines inclined at 5° to one another. If, then, the hori¬ 



zontal distance is carried on 0 H at the scale—in 0 C, for instance 
—the perpendicular erected at C will, by its intersection at D with the 
line corresponding to the angle of elevation observed, give the altitude 
C D, the length of which is found by the scale. This altitude is added 
or subtracted, according, as we have observed an angle of elevation or 
of depression: the height above the ground of the instrument with 
which those angles have been measured must also be added or sub¬ 
tracted. 

(111.) There are many instruments for levelling; the only one 
employed to measure directly the altitudes which we shall mention, is 

Fig. 120. 



the French water-level, because it is easily constructed. It consists 
of a hollow tube, a b, of tin or brass about 3 feet long, with two 
empty cylinders, a d b c, soldered at its extremities, and terminated 
by two glass bottles. A socket, s, is inserted in a tripod. Its use is to 
give a horizontal direction : to that effect it is placed level at sight, and 
water is poured into the tube until it reaches about f of the height 

g 2 










84 


A PRACTICAL COURSE OF MILITARY SURVEYING. 


of the phials. The surface of the water in these bottles determines a 
horizontal direction, H H'. 

To find the difference of level between two points, A and B, station 
between them: send a man to set a levelling-staff at B; look 


Fig. 121. 



along the surface, H H', and read the height, B C; send the same 
or another staff at D, and in the same manner obtain the height, 
A D. The difference of level is given by A D-B C. 

There are several sorts of levelling-staves more or less ingenious, 
but if none is to be had, a pole divided into feet and inches will answer 
the purpose. The pole bearer, when in station, will move up and 
down the pole a piece of white paper, to enable the observer to see 
more easily its intersection with the artificial horizon. In case the 
latter should be too far to read the graduation, when sign is made to 
stop, he will himself read the figure and give it. 

When the ground is very uneven, several stations are necessary; 


Fig. 122. 



in this case we station between s s', s's", &c.; and if m, m, m' represent 
the back measures, n , n\ n" the measures in front, the difference of 
level is found by {m + m' + m" + —) — (n + n' + n "+—). In this case 
a field-book will be necessary to write down these observations, when¬ 
ever the distances are great. 

This level is usefully employed to make a profile of the ground on 
any given direction, an operation occasionally required in the field for 
projects of fortification. We proceed along this direction, as we have 
just now explained, assuming any altitude for the point of departure 
when it is not exactly known. 















LEVELLING. 


85 


(112.) A water-level may even fail us : then it can always be re¬ 
placed by a little ruler, a b, suspended by two strings, c a, c b, having 
a little weight under it to prevent the wind from shaking it. 


Fig. 123. 



When held by the string, the. line a b will give a horizontal 
direction. To make use of it for levelling along A B : Start from A, 
hold the ruler up to the eye, and aiming along its edge, notice to what 
point, b, of the ground the visual ray corresponds. Repair there, we 
shall have ascended a distance=the height of the eye above the ground. 
Start afresh, from b, and in this manner the number of stations made 
between A and B, multiplied by the height of the eye above ground, 
will give the difference of level required. 

(113.) The chain may in some instances serve us as a levelling 
instrument (48), to measure heights, but a clinometer should be pre¬ 
ferred. The next example will serve as further illustration. To find 



the height, A H, of an inaccessible steeple, A, situated on a slope. 







86 


A PRACTICAL COURSE OP MILITARY SURVEYING. 


Measure any line, C D, in any convenient spot, bisect it at 0, 
inarch from D towards A, measuring any length, D E, trace 0 E, and 
produce it of an equal length, 0 F; trace C F, and produce it till it 
intersects the direction O A, in B. Then 0 B=0 A, and distance, 
B A, is known. 

At any point, a, of A B, plant a pole of such a length, that the eye 
at B may see its top in line with H. Measure a B and a h, and 
AH : ah : : AB : aB. 

(114.) The difference of level between any two points may be found 
with the plane table. Beferring to the instrument of Major Fevre (90), 
we find that a wooden plummet in the shape of a ruler can be suspended 
in o. Stationing at one of the points, at A, we hold the table in the 
left hand, and aim along the side, A C, to the second point, B; the 
plummet remaining vertical, the angles poq and D A B are equal. 



If we carry from o to d, a distance, d o, equal to the projection 
of A B, the triangle o g d is similar to BAD, and the line g d 
measures the difference of altitude required. Instead of carrying from 
o to d the projection of A B, we may carry on o m any multiple, M, of 
it, and afterwards holding the table in the right hand, tha-plummet will 
take a symmetrical position, o q', and the distance, n n', will be 








LEVELLING. 


87 


2M times, tlie difference required. The graphical error is thereby 
diminished. 

As, however, it is impossible to reach the point o on account of the 
screw, the distance o p, which is constant, is marked on s s' on the 
edge of the plummet. The multiple of the projection being then 
measured from s to r, the point m is fixed by taking p m=s' r. A 
slit cut through the plummet permits the introduction of the point of a 
pencil to draw the lines o q, o q'. 

(115.) A clinometer has been constructed by Mr. Trinquier to 
obtain not only the angle of elevation, but also the horizontal and 
vertical distances between two points. It is contained in the lid of his 
prismatic compass, P, which is square, and it is kept erect by means of 


Pig. 125. 



a bolt, E. The bottom of this lid, D, is divided into two semicircles by 
a horizontal line, which we may call the fixed diameter* The lower 
























88 


A PRACTICAL COURSE OE MILITARY SURVEYING. 


semicircle is divided into zones of equal width by vertical lines, 
numbered from the centre to the right and left. Another series of 

Fig. 126. 



lines are drawn parallel to the fixed diameter at half the intervals of 
the former and are numbered downwards. 

A semicircle of brass, B, is suspended by the centre, a, round which it 
can move freely until we stop it by means of a spring at the back of 


Fig. 127. 



the lid. It has the same dimensions as the fixed figure: its edge, c d, 
bears the same divisions as the fixed diameter, and its circumference is 
graduated from 0 to 90 on both quadrants. A weight, b, acting as 
plummet maintains the diameter c d parallel to the horizon in what¬ 
ever position the instrument is placed. This movable diameter carries 
two pins in c and d, so that when we see them coincide in looking 



































LEVELLING. 


89 


through the apertures m, m', we know that c d is horizontal, and that 
both the fixed and the movable diameters coincide. Two thin strips of 
metal, s s', are screwed to the sides of the lid; one of them, s, is pierced 
with a vertical and a horizontal slit, the second, s', carries two hairs to 
correspond. The vertical slit and hair serve to take azimuths with the 
compass, and have nothing to do with the clinometer. It is evident 
that if we apply the eye to the slit q and look at an object until the 
slit q, the hair q', and this object be in one line, the fixed diameter will 
be parallel to this line of sight, whilst the movable diameter remains 
horizontal. Thus the divisions of the instrument will always form 
right-angled triangles, similar to those on the ground: the movable 
diameter or hypotenuse represents the distance between two points, 
the fixed diameter or base measures the projection of the distance, and 
the perpendicular shows the vertical distance. An example will at once 
show how to handle this instrument. Suppose that the line of sight takes 
the direction X Y, the angle of elevation is at once given at Q. It is here 


Fig. 128. 



25°. Let now the distance from our station to the object Y be measured 
along the slope X Y, and let it be 220 yards, for instance. Assuming 
each division of the horizontal diameter to represent 10 yards, the 
graduation 22 coincides with the perpendicular 20, showing the pro¬ 
jection or horizontal distance to be 200 yards. The vertical distance is 
read at the extremity of the parallel to the fixed diameter corresponding 





90 


A PRACTICAL COURSE OF MILITARY SURVEYING. 


to division 22. It is line 18, but as the intervals are only half tbe 
vertical ones which represent 10 yards, the difference of level is 
18 x 5 = 90 yards. 

To find the difference of altitude of two points when projections are 
fixed on the plan, we station at one of them and aim at the other. 
Suppose that the plan given is a horizontal distance of 190 yards: we 
find division 19 of the fixed diameter, and see where the movable 
diameter intersects perpendicular 19. If this point of intersection cor¬ 
respond to horizontal 12, the vertical distance is 12x5 = 60 yards. 


91 


CHAPTER IX. 

MILITARY SURVEYING. 

(116.) It has already been said that the first step to be made in a 
military survey is to select and measure a base (43) and by means of 
angles to construct a canvas connecting the important points of the 
ground. As the triangles should be of the equilateral form, it 
is advisable, when time allows, or when the plan is to be made 
with accuracy, to spend a day over the ground and make a pro¬ 
visional triangulation, indicating approximately the form of the tri¬ 
angles, and thereby enabling us to select the points which will serve 
to construct the definitive canvas. 

This preliminary operation is accomplished as follows : we repair 
to the extremity, A, of the base we intend selecting, and draw a line on 
the centre of a piece of paper that will represent the direction, A B, of 


Fig. 129. 



this base; having then placed this line on the same vertical plane with 
its homologous line on the ground as explained before (84), and aiming 
successively with any ruler (82) at the points CDEF, or guessing 
(135) at the angles they subtend, we draw the lines A C, A D, A E, A E. 

Proceeding to B we repeat this operation on another sheet of paper, 


Fig. 130. 

-___ 

E 

\G- 



aiming at the same points as before, and to others if any a?e to be seen. 






92 


A PRACTICAL COURSE OF MILITARY SURVEYING. 


Transporting ourselves to another station, E, &c., we continue to 
Fig. 131. 



protract the angles observed at every station on distinct pieces of paper, 
until we have been over all the ground which we have to survey. 

At home, we assume any length, A B, for that of the base, and 
transfer round the point A all the angles measured in sheet 1st, which is 

Fig. 132. 



easily done by placing A on a and A B on direction a b, and pricking 
with a pin a point on each of the directions A C, A D, A E, A f. 

With sheet No. 2, we place B on b, and B A along the direction 
b a and transfer as explained all the angles observed at B. Several 
points, c, e, d, f, are thus obtained by intersection, and not to lose 
them it is usual to surround them with a little circle. 

With sheet No. 3 we place E on e, and E A on e a, and continue 
to transfer the angles. Thus we obtain the relative position of the 
points of the canvas, and ascertain the form of the triangles. 

(117.) The definitive stations being selected from this provisional 
canvas, we measure the base and draw it at the scale on the minute, and 
afterwards proceed successively to every station where we accurately 
observe and protract the angles. According to circumstances the plane 
table, prismatic compass, or sextant, will be employed for that purpose; 







MILITARY SURVEYING. 


93 


but we readily appreciate the value of the two former. The base, which 
should be in a central position, is measured either by chaining or 
pacing. When time is failing we can procure the base from a map of 
the locality, and the canvas is at once plotted without any preliminary 
operation. The canvas itself might eventually be procured from a 
map, but as the points thus found are generally inaccessible, it becomes 
necessary to determine by means of them the position of accessible 
stations (18, 76, 88). 

The canvas is the most important part of a survey, and we should 
take the greatest care to make it as exact as the instruments and time 
at command will permit; it will in the end save much trouble while 
filling in the details. The objects visible from a long distance, such as 
steeples, chimneys, remarkable trees, peculiar signals, &c., should be 
most carefully fixed on the minute, and besides those we should also 
determine the turnings of high roads, the points of entrance of a road 
through a wood, a village, &c., and the summits of hills, intersections 
of valleys, &c. 

(118.) When the canvas is completed, it is usual to trace on it the 
direction of the true north. If the base has been taken from a map 
ready made, its azimuth is easily found thereon; but if it has been laid 
down from actual measurement, we trace a meridian on the ground 
through the extremity of the base or of any line of the canvas, and 
protract on the plan the angle formed by the two directions. 

To trace a meridian on the ground, plant a staff vertically, and 
Fig. 133. 



describe from its foot as centre several concentric arcs. A little before 





94 


A PRACTICAL COURSE OF MILITARY SURVEYING. 


and after noon observe the course of the sun, and mark the intersections 
of the shadow of the staff with those arcs. Bisect in M, M', M" 
each of the arcs m n, m'n', m"n", &c., intercepted by this shadow, and 
those points M, M', M" belong to the meridian. 

The meridian may also be traced directly on the minute by a similar 
process, by driving a pin, for instance, to replace the staff, but the 
minute should be placed in a position of parallelism (84). 

If there is no sun, or if time must be saved, the prismatic compass 
gives us the magnetic azimuth of a line of the canvas, and we conclude 
the true azimuth by adding or subtracting the variation. 

The polar star may also help us to trace the meridian approximately, 
for it is very nearly in the true meridian when it arrives in the same 

Fig. 134. 


^Folfstar 

f.Eble 


. jC. . 
, *r 


vertical as the star E of the tail of Great Bear. A plummet enables 
us to ascertain the position of verticalism. 

(119.) When a survey is very extensive, several officers concur to 
its execution; the canvas is first made on a single sheet, and is after¬ 
wards transferred to the several minutes, but in order that those indi¬ 
vidual surveys may afterwards agree, the transfer of the points is made 

Fig. 135. 



by means of their co-ordinates referred to two rectangular axes drawn 


















MILITARY SURVEYING. 


95 


across the canvas, representing generally a meridian and its perpen¬ 
dicular. Thus the canvas on M N is subdivided into four sheets; on 
which the details can simultaneously be filled in, and these four minutes 
being placed close together will give the general plan. 

(120.) Having in hand a minute with several points fixed upon it by 
the triangulation, we proceed to fill in the details. 

The prismatic compass is undoubtedly the most eligible instrument 
for that purpose, but one should not exclusively trust to it, because in 
case of accident, and accidents will occur in the field, the operations 
would be interrupted. A previous acquaintance with the plane table, 
or the chain, the sextant, &c., will in such case prove of great service; 
but above all the plane table should be well understood, inasmuch as. 
being replaced by the minute itself (82) it can never fail us. 

To survey the details with a prismatic compass, we station at a point 
from which they are easily reached, a crossing or change of direction 
of roads, the entrance to a village or wood, the corner of a wall or of an 
inclosure, &c. We determine on the minute the projection of that 
station by taking two or three bearings on the points already given 
(76), and we proceed as described for traversing; we frequently check 
our work by taking bearings on the points we have previously found; 
and by pacing the distance at every station to the various details, we 
successively introduce them, and even draw them at sight between two 
stations sufficiently close to each other. The method of intersection is 
to be had recourse to whenever possible. 

To fill in with the plane table, we select the same points, and find 
our station as explained (84, &c.), introducing the details by intersec¬ 
tion, by chaining or pacing, and traversing on the chief direction. 

With a box sextant the operation is more troublesome, but the 
principle is the same. 

(121.) Whatever instrument we employ, we must frequently verify 
our position on the survey by means of those points of which we are 
certain, otherwise the errors will rapidly accumulate. 

We lay down the trees, embankments, ditches, rocks, &c., and 
indicate the various kinds of culture by initials, to figure them after¬ 
wards according to the conventional signs. 

The chief objects to determine exactly among the details are the 


96 


A PRACTICAL COURSE OF MILITARY SURVEYING. 


roads, paths, openings through forests, rivers, rivulets, lakes, pools, 
fountains, streets, outline of towns and villages, isolated buildings, 
mills, churches, castles, bridges, &c.; and while 'filling in these details 
we note in our pocket-book all the information that will subsequently 
enable us to write our report. 

For rivers, we follow one side by traverse , and determine the other 
by intersections; for rivulets we also fix some points of their course by 
means of bearings, and have recourse to the cross-staff (105) when 
advantageous. 

For towns or villages, the outline is first surveyed, and the entrances 
of the chief streets accurately fixed: then we engage in one of those 
thoroughfares, and while traversing we protract every detail by 
pacing the perpendiculars dropped from them to the direction we 
follow. After this we start from a central point, such as a square, a 
church, &c., to the various outlets. The yards, gardens, &c., are 
subsequently drawn at sight. The masonry is marked by a thick line, 
and the houses are shaded, so as not to be confounded afterwards with 
the yards. 

The woods and forests are plotted in the same manner: first the 
perimeter, then a road, then the various outlets. 

' It would be impossible to enter into the never-ending particulars 
of the filling in the details. A day spent in the field with a brother 
officer well acquainted with the practice of military surveys, will do 
more for the instruction of the beginner than volumes of text. The 
principles of planimetry are both simple and few; the instruments 
employed are easily handled; but it is left to the sagacity of the officer 
to make the best use of those tools by an intelligent application of the 
methods previously described. Nothing is more simple, and the 
problem becomes still easier if the surveyor brings to bear on his work 
all the accuracy allowed by the instruments he employs. Accuracy is 
a saving of time and trouble. 

(122.) To complete the survey it is necessary to represent the 
undulations of the ground, and to give the relative height of every 
point of its surface, together with the direction of the acclivities and 
declivities. 

To effect this we begin by determining the altitude of a few of the 


MILITARY SURVEYING. 


97 


points obtained in planimetry, in order to form wbat we may call a 
canvas of levelling'. If the altitude of one of those points is known, 
we obtain that of the others by means of the angles of elevation (110). 
If it is not known, we assume a certain value for it and calculate the 
others; for in military surveys all that we require is the relative height 
of the different points, and it matters but little whether it is possible or 
not to obtain from a map or any other source the truQ elevation above 
the level of the sea. 

(123.) Having carefully established this canvas, we proceed to fix the 
position of the highest and lowest points of acclivities, that of ridge 
lines, thalwegs, cols, and of all points at which there is a change in the 
intensity of the slopes, which have not already been determined in 
planimetry. Their accurate position on the minute is indispensable 
for fixing the projection of their respective distances. 

This done, we station with the clinometer at the points of known 
altitude, measuring the angles of elevation or depression, and by means 
of the formula H=D tang, a, or the table (110), or even by a simpler 
process (112), we find one by one the altitudes of the various points 
which have been enumerated, and it is advisable to verify the altitude 
of the important points by means of two others. 

(124.) When this is completed, we figure the undulations by the 
contours, an operation which is much simplified if we have, while 
stationing on any point, indicated the direction of the slopes. In fact, 
an officer accustomed to survey will have done so even in plotting the 
planimetry. The best way to mark this indication is to look in four 

Fig. 136. 



perpendicular directions, and figure by little arrows the direction 

H 






98 A PRACTICAL COURSE OF MILITARY SURVEYING. 

of the slopes ; a few hachures more or less thick, or a few con¬ 
tours more or less close as the slope is more or less steep, will suffice. To 
estimate the direction and steepness of a slope, we must stand on it, 
and examine only a small extent, otherwise the effects of perspective 
will lead to error. 

The four directions are quite enough j if the four are descending 
we are on a hill; if three descend and one ascends, we are on a ridge 


Fig. 137. 



(Tig. 137). If two contiguous ones ascend and two descend, we are 


Fig. 138. 



again on a ridge. If two alternate ones ascend and two descend (Fig. 138), 




MILITARY SURVEYING. 


99 


we stand on a col. If three ascend and one descend (Fig. 139), we are on 

Fig. 139. 



a thalweg. Lastly, if the four ascend (Fig. 140), we are in a hollow. 
These rough indications, with which we soon become familiar, are 

Fig. 140. 



exceedingly useful in helping to connect the undulations of the different 
stations ; and an experienced surveyor will, by their means alone, and 
without ever seeing the ground, represent its surface tolerably well. 

(125.) Two methods are in use to trace the contours. When they 
must be traced with rigorous exactitude, as it sometimes happens in 
the survey of a site intended for fortifications, we have recourse to a 
water-level. To be clear, let us suppose that the altitudes of A and B 
(Fig. 141) have been found to be respectively 80 and 10, and that the 
equidistance (21) is 10. Between A and B there will be six contours. 
Divide A B into seven parts having altitudes, 20, 30, 40, 50, 
60, 70, and plant a staff at each. Now, stationing at any point, P, 
set the level right, send a man with the levelling-staff at A, and note 

h 2 


100 


A PRACTICAL COURSE OF MILITARY SURVEYING. 


the reading. The man moves afterwards in the vicinity of A, until 
the same reading he again in sight with the level: the point C, where 


Fig. 141. 



this occurs, is evidently on the same level with A, and the man plants 
a stake thereat: on he goes, and as many points as are wanted are 
fixed in this manner. The same operation is repeated for contours 70, 
&c. Having thus traced the contours on the ground, they are plotted 
on the minute, with the help of the prismatic compass to take the 
hearings of the stakes. 

This method is long and tedious, therefore the second will be pre¬ 
ferred as more expeditious, and sufficiently accurate for general pur¬ 
poses. 

(126.) Suppose that the altitude of the points a, b, c, d, e, &c. (Fig. 
142), has been ascertained (122), and that the equidistance=10 yards. 
Join those points by straight lines. The point a is on a contour, but h 
is not, and there will be five contours between it and a. Divide a h 
into six parts, five of them equal, and the rest only (Euclid, 
p. lvi.), the contour will pass through the points of division, 
Again, take b c, and divide the line into six equal parts, if the sketch 
(124) indicates a uniform slope. Along a d the sketch implies a 
greater declivity towards a ; divide, then, a d, by sight, into six unequal 
parts, the smaller being nearest to .a; divide m n into three equal 










MILITARY SURVEYING. 


101 


parts, and if the sketch indicates a continuance of the same slope above 
n and below m, carry another division beyond those points, and so on. 

Fio. 142. 



The points of same altitude are afterwards connected by a continuous 
line. 

(127.) The clinometer of Trinquier will here be found very con¬ 
venient. By means of the pins of the movable diameter (115) which 
determine a horizontal line, we can trace one contour as already ex¬ 
plained (125). Let ABODE be this original contour, and let 

Fig. 143. 



the equidistance be five yards. Stationing at A we aim with the 
horizontal slit along the steepest line of the slope (or the less steep, 
as the case may be), as far as we can see the dip uniform. Let the 








102 


A PRACTICAL COURSE OF MILITARY SURVEYING. 


angle of depression be 25° (Pig. 128). The parallel 10 intersects the 
movable diameter at a point corresponding to perpendicular 11 of the 
fixed diameter. This shows that for a distance of 110 yards the vertical 
fall is 10x5=50 yards, or that for 11 yards measured horizontally the 
dip is 5 yards. Hence, if on direction A A' of the dip, placed on the 
plan by means of the compass, we take parts of 11 yards each, we 
obtain as many points belonging to the contours required. Stationing 
now at B, we repeat the same operation: if the parallel 10 intersects 
the movable diameter at a point corresponding to perpendicular 20, 
then on B B' the contours will be 20 yards apart, and so on. 

(128.) The operations of levelling as described here should be made 
by beginners after they have completed the planimetry: but when 
they have, by means of practice, acquired a fair acquaintance with the 
forms of the ground, they may venture to conduct planimetry and 
levelling abreast. In military surveys they will be expected to do so, 
because the exactitude of the contours is not necessary, the chief 
thing consisting in indicating the relative heights, so as to distinguish 
those practicable to the three arms from those that are not. There¬ 
fore, whenever making a station in the field, we must sketch the 
features of the ground around it, and when repairing from one station 
to another, endeavour to connect those indications by slight touches of 
the pencil, to be afterwards modified when the clinometer shall have 
come into play, and given the altitude of a few stations on the thal¬ 
wegs, ridges, summits, cols, &c. Let us here more than ever beware 
of the field book; never trust to memory if we can help it, and con¬ 
stantly draw the features from nature. There lies the real study of 
topography. 

(129.) When a survey is made for a special purpose, it is customary 
to compile a memoir to complete the description. The table (141) 
contains all that is necessary. 


103 


CHAPTER X. 

MILITARY SKETCHING. 

(130.) It very seldom occurs that in the field we have either the 
time or the means of executing regular surveys; and as plans are 
necessary to guide the movements of troops, prepare their encampments, 
select positions, combine attacks on field works or passages of rivers, 
&c. &c., it becomes indispensable for officers on the staff to make those 
plans or sketches either without instruments, or merely with those that 
they can construct themselves on the spot. 

Nothing is impossible, especially in topography ; and whatever be 
the circumstances under which an officer is placed, he should never 
give up an attempt as useless until he has tried. And if he tries, he 
will succeed. 

Referring to the foregoing chapters, all that is required to make a 
plan is to measure distances and angles. Eor distances, we have three 
means—our pace, the trot of a horse, or our watch—the first of which 
cannot fail. For angles, if a prismatic compass or a sextant cannot be 
found, a plane table can be improvised, and it is indeed a capital 
instrument. A cross-staff and a clinometer are made in a few minutes. 
If we employ this rough table a pin fixed into it shall provide us with 
a sundial which will still simplify the operation. With paper, pencil, 
india-rubber, and a knife, we have the wherewithal to proceed. 

A previous acquaintance with the principles of topography, and a 
fair amount of practice in regular surveys are indispensable, since in 
every sort of sketch the art consists in making the best possible 
attempt at imitating the regular process, according to the resources at 
hand. A few words will be sufficient to point out what is to be done 
when we have contrived to extemporize our instruments, and have 
time enough to take measurements, or when, being hurried, we have 
scarcely time enough left for that purpose. 


104 


A PRACTICAL COURSE OP MILITARY SURVEYING. 


(131.) The first step to be taken is again to select a base and form 
a canvas. Sketches are generally made at the scale of 4 inches to 
the mile, but we adopt the scale of paces and construct it at once. If a 
map can be obtained we transfer the base as well as the canvas on 
our minute, selecting for vertices of the triangles the steeples, windmills, 
bridges, or crossings of roads. But as this is possible in Europe only, 
we are almost always compelled to measure the base and to construct 
the canvas by one of the methods which have been explained: if the 
country is woody or barren we plot the triangles by pacing—a long 
but then indispensable process, which can nevertheless be simplified in 
employing men to signal remarkable trees or to stand for points of 
triangulation. 

(132.) The details will afterwards be filled in, and as this operation 
'will be $o much the easier when the canvas is well and closely 
executed, we could not pay too much attention to its construction. 
The methods of intersection in open countries, that of traversing in 
woody ones, are successively or simultaneously employed. Starting 
from one station we proceed to the next, drawing details at sight, 
right and left of the direction we follow, occasionally climbing a tree to 
discover them better. 

With regard to the representation of the relief, the canvas contained 
some points on the characteristic lines of the undulations, thalwegs, 
ridges, and on summits. An arbitrary altitude being assumed for one 
of those points, the height of the others will be ascertained by means 
of the clinometer. The details of the relief will be plotted by figuring 
at every station the lines of contour and the directions of the acclivities 
(124). It would take more time to describe all the operations of such 
a survey than to make one. We shall therefore confine ourselves to a 
few remarks. 

(133.) The details of every triangle are filled in by following first 
the direction of the perimeter, then a direction either road, thalweg, 
or ridge, running across it, laying down the details at sight, subdividing 
the triangle into two parts. Those are again subdivided in the same 
manner until the parts become sufficiently small to permit drawing at 
sight whatever they contain. 

We should not hurry in attempting to represent too much at 


MILITARY SKETCHING. 


105 


a time on both sides of the direction we traverse; it is far better 
to indicate them slightly at first, and definitively plot them when 
their position has been verified by that of the other roads or direc¬ 
tions between which they are contained. These roads should be 
traced according to their general direction; this is important, inasmuch 

Fig. 144. 



as there is a tendency among beginners to exaggerate the windings 
and to represent the road A B as a b. 

For a village, it is advantageous to make a preliminary reconnoitring 
from the top of a high building or a steeple. We trace its chief 
street; then, if possible, two streets at right angles : after this, we 
take the perimeter of each part, and subdivide it till the details can be 
drawn at sight. The same of a wood. 

In figuring the relief, we should remember that we have a great 
tendency to exaggerate the importance of the acclivities on which 
we are placed, especially when the ground presents slopes alternately 

Fig. 145. 



gentle and steep; so much so that the slope B A is often estimated to 
be on the opposite, A' B'. 

When following a thalweg, T, slightly pronounced, having for 




Fig. 146. 














106 


A PRACTICAL COURSE OF MILITARY SURVEYING. 


instance a mere depression of two yards, we are inclined to exaggerate 
it as in T'. ^ 

We are also invariably inclined to open the valleys too much, 
and this may be avoided by determining carefully the position of 

Fig. 147. 



the lines A B, A' B', on which the slope of the sides changes its 
direction. 

(134.) When the enemy is close by, a survey at sight or a 
sketch is the only representation that can be made when any infor¬ 
mation is needed respecting the ground, and as time becomes 
precious, the foregoing operations can no longer be made. Here the 
coup cTceil is indispensable, and if an officer has not by a long practice 
become familiar with valuing distances and angles at sight, he will 
fain attempt such a reconnoitring. 

Although such surveys generally embrace but a limited extent, 
since they would otherwise be far too inaccurate, yet a method of 
measurement should be adopted, because perspective would tend to 
accumulate errors upon errors—there being no absolute, but only 
relative, dimensions for the eye. 

The means employed differ but little from those employed in 
topography. We select and measure a base, and connect it with the 
different points of the surface by climbing a tree or ascending a cul¬ 
minating spot. Or we select three conspicuous objects, measure by 






MILITAKY SKETCHING. 


107 


time their respective distance, and plot the triangle at the scale. 
Starting from one of the corners, we advance towards the other, draw¬ 
ing at sight all the angles. Having done so round all the perimeter, 
we proceed to the interior. The undulations are figured at the same 
time, hut, as it is only necessary in this case to “ accuse” the relative 
heights, this is done by making the hachures thicker when the slope 
is steeper. Numbers 1, 2, 3 may be inscribed on the minute to denote 
the heights in relation to their importance. Great attention is paid in 
distinguishing the acclivities practicable to infantry, cavalry, and 
artillery from those that are inaccessible. 

Perspective leads to many illusions; a steep hill appears nearer 
than it is. In some instances distance seems greater at dark or in foggy 
weather—a smooth object appears nearer than a rough one; the di¬ 
mensions seen from above seem smaller than those seen from below. 
No attempt should, therefore, be made to guess beyond a mile. 

(135.) The officer who is liable to be called on to execute this sort 
of survey should exercise his sight, and know at what distance he no 
longer distinguishes a man, a horse, a tree, a house, &c.; this alone 
may help him greatly. 

Angles must be guessed at. Among the many means employed to 
obtain them, we may notice the following:— 


Fig. 148. 

e 




T 



T> 


4- 


c 

■ ATT? 

: >1 

K " -- Iz 


V 




y 


N j 


1 



Two pieces of wood, two rules, for instance, are fixed together at 
right angles in a: the side ab=ac=ad, and ae=Gb a=|ca. Pins 
being planted at b, e, c, d, this contrivance will be employed 
as the staff cross (97); it gives several angles—bde=edc=cbd= 










108 


A PRACTICAL COURSE OF MILITARY SURVEYING. 


b c d=45°; eb c=e c b = 30°; bed=dec=60°; ebd=ecd=75; bdc 
90°; b e c=120°. It is the winJcel Jcreutz of tbe Germans. 

A foot-rule with a hinge, or a piece of paper folded, may serve to 
measure and trace the opening. A square piece of paper folded in 


Figs. 149 and 150. 



half along AB, then folded in i, &c., gives angles of 90, 45, 22i, 
Hi degrees; and those of 78f, 67i, 56£, 33f, are obtained in opening 
all but one or two, &c., of the folds. 

Fig. 151. 



The forefinger and thumb of the arm extended to their utmost 
stretch subtends about 11°. 

Fig. 152. 



These auxiliary means will guide the observer, but he should exer¬ 
cise himself in guessing at a few angles round the whole space, and 










MILITARY SKETCHING, 


109 


correcting his valuation by the excess of their sum over 360°. Taking 
first 4 angles, then 8, then 12, his eye will gradually gain experience. 
Indeed, it is surprising with what accuracy some practised officers 
value a series of angles at sight. 

(136.) Among the many cases that may occur, the reconnoitring 
of a road (77) through which a convoy or a detachment will have to 
pass, happens frequently. It is accomplished by traversing, guessing 
at the angles formed by the windings, and sketching the details at 
sight within a few hundred yards on both sides. This sketch, or 
itineraire, as it is called, is accompanied by a report giving the 
distance between the most remarkable points, such as villages, defiles, 
bridges, ascent, descent, change of direction, buildings, cross-roads, 
&c. It will state the time employed to perform the journey, give the 
width of the road, indicate its nature, &c. The objects having military 
importance should be described: villages, houses, rivers, bridges, fords, 
&c.; the accommodation for man and horse either on the march or in 
permanent quarters likely to be found in the villages; the means of 
transports, such as horses, carts, ferries, &c.;—in a word, everything 
we can learn or see should be noted. (See 141.) 

(137.) It may happen that an officer has not even the time to survey 
in this manner, and that he is placed in such a position that he cannot 
ostensibly make use of his pencil. This most generally occurs under 
very important circumstances—in the proximity of, if not under the 
very eye of the enemy. To memory alone he must trust; therefore 
it is indispensable that he should understand thoroughly the object of 
the reconnoitring, in order to concentrate his attention on those points 
of the ground which possess importance. He should notice the time 
he took to walk or gallop to the chief points. He examines the state 
of the roads, the direction and inclination of acclivities, the rivers, 
rivulets, and their embankments, &c. &c. Returned at the camp, he 
should plot the chief objects in traducing the time into distance, and 
group the details around them. This sort of survey is closely con¬ 
nected with military art—in fact, it belongs to it. 

(138.) A rough sketch may even be had from mere indications, pre¬ 
viously to entering a country occupied by the enemy : spies and inha¬ 
bitants, especially guides, hunters, carriers, muleteers, shepherds, &c., are 


110 


A PRACTICAL COURSE OF MILITARY SURVEYING. 


examined separately and cross-questioned as to the roads and paths, 
the places they lead to, the obstacles, defiles, woods, hills, rivers, 
marshes, bridges, &c. The sketch is made under the eyes of the 
informer, marking the distances in time, and it is successively rectified. 

(139.) Reconnoitring is the ensemble of the operations necessary to 
obtain information on the nature of the country on which the war is 
carried, on the resources it affords, or on the forces and positions 
of the enemy. 

Generally, reconnoitring will consist of two distinct parts, 1st, a 
plan or sketch ; 2nd, a report. 

According to circumstances, the sketch will be one of those we 
have described. 

As for the report, it should contain a brief account of all that bears 
upon the end in view, distinguishing most scrupulously that which has 
been seen from the information collected from various sources, but not 
verified personally. 

An officer entrusted with a reconnoitring receives some special 
instructions from his commanding officer: to them he must implicitly 
conform, without attempting to swell his report by details unconnected 
with the purpose of the reconnoitring. It is not an easy task, to seek 
for, to take, and to collect the information required; it implies a vast 
experience : therefore, to accomplish it with credit, we should during 
peace prepare ourselves by several exercises on the ground, and by 
reports on some special cases connected with the arm of the service to 
which we belong. 

To take and collect information at home is difficult, because when 
the inhabitants perceive officers engaged in the act, they grow sus¬ 
picious lest some new billeting or some tax be imposed upon them: 
but in a hostile country it is far worse—so much so that they conceal 
all they can, and invariably affirm that the “ environs” of their village 
are impracticable; hoping thus to deter the troops from approaching 
them. Even when of good faith they give out to be practicable the 
regular roads and paths only, and consider as great obstacles the 
ploughed lands, hedges, ditches, &c.; so that it becomes necessary to 
multiply the investigations in order to ascertain the truth. 

While executing the plan or sketch, we collect and note all that 


MILITARY SKETCHING. 


Ill 


we see: we question guides, shepherds, carriers, as well as mayors, 
"bailiffs, &c.; examine the maps in existence, the statistical, historical, 
and military works written on the country under investigation. If 
none can he found, we endeavour to extract statistical information 
from the inhabitants themselves—this skilfully and indirectly—avoid¬ 
ing to frighten them or to rouse their suspicions. To this end a fair 
knowledge of the language of the country is indispensable. 

(140.) For officers who have not yet acquired some experience in 
writing reports on reconnoitrings, we give a table of the different 
subjects to be examined in the most general cases, as adopted in the 
French staff. They are enumerated in the order in which they should 
be treated. It will be sufficient for the most extensive memoirs, and 
for any special case, such as the reconnoitring of rivers, roads, &c. The 
points to which attention should be directed are found under the proper 
heading, if they are not mentioned in the order given at starting. 

This report is written legibly, with conciseness and lucidity. 
Proper names should be carefully spelt. The order in virtue of which 
the operation has been made is transcribed at the head of the manu¬ 
script, which is made up as a report, not as a letter, and signed by the 
officer. 

§ I. 

Physical Description. 

(141.) Geographical Position of the Ground reconnoitred. —Approxi¬ 
mative limits between which the ground reconnoitred is enclosed. 
Latitude, longitude, and if possible, altitude of the chief point; 
general watershed; boundaries of the coast, of the watershed; principal 
basin to which the ground belongs. 

General Configuration of the Ground. —General aspect; mountainous, 
hilly, or level; open or wooded; of easy access, or intersected with 
obstacles, hedges, ditches, enclosures, walls, rocks, &c.; covered with 
bares or heath; dry or marshy. 

Basins , Orography. —Basins in which the ground lies. Chains of 
mountains and their ramifications; chains of hills and of secondary 
heights; of what description. Table-lands, their form and area. 
Direction of the watershed lines; remarkable points through which 


112 


A PRACTICAL COURSE OF MILITARY SURVEYING. 


they pass ; greatest altitude; table-lands or heights across which they 
run. ^ 

Valleys, vales, ravines, defiles: their dimensions; height of the 
sides, and steepness of their acclivities; great undulations which 
destroy their regularity or obstruct the circulation; eminences or 
buttresses narrowing or running across the valleys; forests; lakes; 
marshes; &c. 

Plains.—Level, undulated, intersected with hills, ridges, bares, 
marshes, &c. 

Maritime or fluvial islands.—Their dimensions ; mountainous, flat, 
marshy, or sandy; wooded; cultivated or barren; inhabited or not; 
towns, villages, anchorages; to be described as a continent when their 
surface is uneven; floating islands. 

Hydrography .—Itivers and streams running across the ground 
reconnoitred; their source; total length of their course; chief towns 
situated on their banks ; their mouths or confluences ; principal tribu¬ 
taries. 

On the ground reconnoitred itself: breadth and depth; variations 
they are exposed to at different seasons; parts where the river is 
fordable, and its depth; variations of the bed; places where, the 
stream branches off; importance of the branches; height of the banks; 
fall per mile; sudden variations in the channel, falls, rapids, eddies, 
rocks; velocity per hour; periodical or accidental rises; their cause; 
time at which they take place; their height above low-water mark. 
Inundations: how far they extend in the valley; mention of extra¬ 
ordinary floods, and the places which suffered most; how to prevent 
their recurrence; dams, sluices, &c. Nature of the bottom of the river: 
rocky, gravelly, sandy, muddy. Nature of the banks: their form; 
flat, gently or rapidly sloping, abrupt, overhanging; height above the 
water; covered with stones, woods, meadows, reeds, or gardens. Com¬ 
mand of one bank over the other; constant or alternate. 

Canals : their name; where they lead to (see § III.). 

Lakes : their dimensions; nature of the bottom and of the banks; 
fordable parts; navigable parts; ports, capes, isthmuses, and other 
peculiarities. 

Ponds : artificial or natural; permanent or not; easy to empty or 


MILITARY SKETCHING. 


113 


otherwise; if the bottom be practicable for troops; produce of 
fisheries, cultivation; influence on the health of the inhabitants. 

Marshes: produced by streams or by springs ; covered with water 
or mud; their extent; if there be any secret or open communication 
across; possibility of draining them. Bogs : their extent; passable or 
not; if turned to any account. 

Swamps, pools: how made use of by the inhabitants; their 
influence on salubrity. 

Fountains and springs: whether numerous and of abundant 
supply; potable, saline, or muddy water; chief ones to be indicated; 
their temperature, when it differs sensibly from that of the atmosphere; 
use the inhabitants make of them ; remarkable peculiarities; inter¬ 
mittent and spouting fountains, &c. 

Cisterns, artificial or natural wells : if they give a sufficient supply 
to the inhabitants. Artesian wells; their depth; abundance and 
quality of the water. Pits. 

Sea Coasts. —Configuration of the coast: cliffs or downs; their 
height and shape; if worn away by the sea; marshy, gravelly, or 
sandy shore; even or undulated beach; natural ports, harbours, 
anchorages, roadsteads, creeks, bays, &c. ; points favourable for 
landing; advantages for navigation; works of art constructed to 
resist the encroachments of the sea; depth below which the vessels 
cannot enter the port; sands and bars near the coast and at the 
mouth of navigable rivers—this mouth to be described; difficulties 
attending the entrance of vessels into, or their egress from, the river, 
either on account of the ground or the winds and tides; mention 
if the bars are changing, and if the passage is more practicable at 
one time than at another; lights and signals, either extant or to be 
established. 

Nature of the Soil at the surface or at different depths. Grottoes 
and caverns ; their extent; to what account they could be turned. 
Subterraneous streams and lakes. Geological composition and mean 
thickness of the vegetable soil in the plains and on the acclivities. 

Volcanoes, either extinct or in activity; volcanic formations. 
Craters, their situation, height, and shape. Basalts, lava, dross, &c. 

Ores of every description, either under work or not. Mines; 

i 


114 


A PRACTICAL COURSE OF MILITARY SURVEYING. 


coal mines; their depth, number, and thickness of the strata; quality 
of the products. ^ 

Quarries of marble, stone, chalk, gypsum ; those that are worked; 
quality of the products. 

Mineral and thermal springs; nature and quality of the water; 
the account it is turned to. 

Salt pits ; salted springs ; salt marshes. 

Aerography. —Climate; warm, cold, dry, damp. Mean barometric 
pressure. Temperature of the various seasons; mean temperature; 
greatest cold; greatest heat. 

Number of wet days; mean quantity of rain falling in the year; 
how long the snow remains on the ground; rivers which freeze so as 
to hear loaded carriages. 

Prevailing winds. Pogs. Properties of the air and water with 
regard to the health of men and animals. Endemic diseases; causes 
of insalubrity; how to remove them. Meteorological facts—Violent 
and frequent storms, hail, waterspouts, &c. Plants and animals 
peculiar to the climate—Eye, wheat, rice, vines, orange trees, cochineal, 
&c. Forests—Fir trees, &c. Eace of men, of mammalia, reptiles, &c. 
Tides—Their chief peculiarities; limits of high and low water in the 
ports and the rivers. 

§ II. 

Statistics. 

Political and Administrative Divisions. —Ancient provinces of which 
the ground reconnoitred has made part. Administrative, judicial, 
ecclesiastical, military, maritime, and financial circumscriptions. 
Counties, departments, cantons, provinces, districts, unions, parishes. 
Courts of appeal and sundry tribunals. Dioceses, consistories. 
Universities, academies, consulships. Sundry services—Postal ser¬ 
vice, high roads. Mines. Woods and forests. Custom-houses for 
direct and indirect taxes. Divisions or military stations—Artillery’s 
head quarters; engineers’ head quarters. Maritime prefectures, dis¬ 
tricts, and quarters. 

Population. —Total population of the canton, parish, district, or 


MILITARY SKETCHING. 


115 


other circumscription. Distribution of the population between the 
towns and country; between agricultural and operative pursuits; 
between mountainous and level countries. If the population is in¬ 
creasing or decreasing. Comparison between the existing and a 
previous state. Causes of the movement of the population. Number 
of inhabitants per square mile ; number of families. With regard to 
recruiting, compare the number of men with the amount of the popula¬ 
tion. Proportion of men declared fit for service to those examined. 
Average height of recruits. Proportion of men fit for the special 
arms of the service—artillery, cavalry, &c. Height, physical constitu¬ 
tion, character, manners, way of living and dress of the inhabitants. 

Differences or homogeneities between the inhabitants. Sympathies 
or antipathies between divers classes of the population, and divers 
localities. Aptitude of the people for war, arts, sciences, commerce, or 
agriculture. Emigration—Workmen going to other countries, or 
coming from neighbouring states; for agricultural or industrial pur¬ 
suits ; extent of emigration. 

Militia, Yeomanry .—Organization into legions, regiments, battalions, 
squadrons, or companies of cavalry, infantry, artillery, firemen. 
Force per county, district, parish, or other circumscription. Number 
of men forming part of the reserve of the army with unlimited leave of 
absence. Maintenance and state of the armament at the charge of the 
states, communities, or private persons. Clothing. Parts of the militia 
wearing uniform. Degree of [military instruction. Aid which the 
armed population would afford in case of need. 

Language .—Languages and dialects ; parts of the population who 
speak them. Usual way of spelling the names of places; their pro¬ 
nunciation, when it differs from the ordinary language; etymology of 
the names of the principal places. Cbaracteristic words to be found in 
the language of the country. Examples. 

Religions .—Divers sects; number of inhabitants comprehended in 
each; their reciprocal disposition. 

Public Instruction .—Degree of instruction of the different classes of 
the population ; proportion of literary persons. Schools of all sorts. 
Literary wealth of public libraries. Universities. Academies. Learned 
societies. 

i 2 


116 


A PRACTICAL COURSE OF MILITARY SURVEYING. 


Public Buildings. —Churches or temples, castles, town-halls, courts 
of justice, colleges, seminaries, museums, libraries, exchanges, markets, 
light-houses, prisons, &c. Kemarkable houses or buildings; their con¬ 
struction or their historical importance. Their use and capacity. 
Objects of art esteemed. 

Houses. —Different habitations, country houses, farms ; their general 
distribution and size; if built of stones, bricks, earth, wood, &c.; 
tiled, or thatched. 

Resources for Lodging Troops. —Estimate of the resources for men 
and horses. Eor troops on the march or quartered; whether in mili¬ 
tary buildings or other public establishments, or in private houses; 
large buildings fit for the reunion, in a case of emergency, of a large 
body of men or horses. Localities in which small buildings only are 
to be found. Military establishments, hospitals, parks, magazines, &c. 

Materials of Construction employed in the Country. —Marbles, stones, 
bricks, udders, &c.; timber and other woods ; metals; quarries whence 
the materials are extracted. 

Statistics of Towns. —Capitals of counties, departments, fortified 
places, garrisoned or maritime towns, and all towns having more than 
3000 inhabitants. Situation—Advantage of the position of the place, 
whether as a fortified place or a centre of industry, commerce, &c.; 
as a seaport, on a rjver, on a railway, at a cross-way, in a fertile 
country, &c.; its distance from neighbouring towns; aspect of its 
buildings in general; their mode of construction, resources which 
they would offer for the different military services. Enclosed or open 
towns ; shape of the enceinte ; ancient or modern fortifications; walls; 
enclosures; divers authorities who sit in the towns; details of the 
population; on the various public establishments; distribution of the 
waters j industry; commerce ; celebrated men of the country. 

Particular statistics of fortified places; system of fortification; 
number of fronts of the enceinte, outworks, ravelins, counter-guards; 
detached works—their form and importance ; if the place is protected 
by a river, by inundations, marshes, escarpments, &c. Military build¬ 
ings bombproof; casemates, resources offered for all military services 
by private buildings and houses. 

Agriculture. —State of the agriculture of the country; general 


MILITARY SKETCHING. 


117 


aspect of the situation ; progressing or falling off; quality of the soil, 
wheat, rye, or barley land; vineyards, meadows, woods, &c. ; high or 
small farming; methods of cultivation, whether by horses, cattle, or 
hand ; harvest rotations; customary crops of the land; artificial 
meadows ; varieties of agriculture; proportion of the sowing to the 
reaping; produce per acre of cultivated lands, meadows, vineyards, 
orchards; mention the various products—hemp, linen, oleaginous plants, 
beetroots, tobacco, &c.; ratio between the production and consumption. 

Woods and Forests. —Forests of public domains ; public and private 
woods; what natural productions predominate ; high forest-trees, 
copse, or underwood ; regulations adopted for cutting; statement of 
the size and condition of the forest; thickets, glades, cultivated lands, 
meadows, ponds, and habitations which they contain; their products ; 
practicable or not for troops, for artillery ; cross-roads, trenches, water¬ 
courses, ravines, ditches ; wood fit for ship-building, or cooperage. 

Cattle. —Different races of horses; the breed progressing or de¬ 
creasing ; qualities and faults of these races; approximate number of 
the kind fit for military service ; saddle and draught horses; paddocks, 
stallions’ depots; number of horses they furnish; mules and asses in 
the country; bovine race ; number of heads of this race compared 
with the population and the wants of agriculture; its qualities ; fleecy 
beasts ; existing races in the country; approximate number of heads 
or of flocks. Goats, only when they are in flocks. 

Products of the poultry yard, the chase, and fishing (when com¬ 
mercial) ; fowls, pigs, game, fish ; butter, eggs; dairies, cheese-markets, 
bee-hives, oil, fruits, &c. 

Industry. —Hand-mills, wind-mills, water-mills, steam-mills—their 
situation and productions; other mills; oil-mills, tan-mills, saw-mills, 
&c.—Paper factories; their production; hand or mechanical fabri¬ 
cation ; founderies and metal works; salt-pits; wool, cotton, linen, 
silk, hat, rope, tan, &c. Factories—china, pottery, bricks, tiles, &c.; 
works—their importance; number of workmen they employ; works 
made by hand, with horses, water, steam. Annual natural productions; 
annual time of rest. 

Local measures of length, superficies, wegiht, capacity; their rela¬ 
tion to standard measures. 


118 


A PRACTICAL COURSE OE MILITARY SURVEYING. 


Commerce. —Agricultural, industrial, native, exotic productions. 
For consumption, importation, exportation,<transit; docks, warehouses, 
&c. Annual variations of import and export; fairs and markets for 
grains, beasts, &c. At what time they take place; their importance. 

Public Revenue .—Direct and indirect taxes ; custom-houses, &c.; 
outline of the working of the establishment of taxes; revenues from 
domains belonging to the State ; do. of the branches of industry and 
commerce of which the State reserves to itself the monopoly; re¬ 
sources of credit. 


% III. 

Communications. 

General Outline. —Network of the communications; high roads of 
divers classes, roads more or less numerous, more or less practicable; 
railways; navigation ; telegraphs. 

Land Communications. —Details concerning each of the high roads 
most important for military operations which are to he mentioned in 
the Memoire; general direction, breadth; paved, strengthened with 
flints, or, in the old way, on natural earth; sided with trees, hedges, 
ditches, walls, poles; hollow or banked up; slope for the drag; low 
parts which could be v overflowed; other causes for accidents ; defiles ; 
facilities or obstacles for waggons; distance between one town and the 
other, and to those to which the road leads ; how frequented; post 
inns, public vehicles, waggons. Means for repairing to be found in 
the country; parts of the road running upon old Eoman ways. 

Roads of Second Order (?) —Principal details of the preceding article 
according to the military importance of the routes. Divers routes— 
on fascines, on ice, &c., &c. Neighbouring roads fit for waggons as 
distinguished from those merely destined for beasts of burden or foot 
soldiers. Footpaths. 

Railways , either constructing or worked ; principal towns they pass 
through; where they end. Branches. Importance of a terminus as 
a point of concentration. Lines, with one or two sets of rails. Dis¬ 
tance from one terminus to the other; total length. Slopes or inclina¬ 
tion of the ways. Obstacles that they pass—Fivers, mountains. 


MILITARY SKETCHING. 


119 


forests, &c. Appointed time for the journey. Mode of construction— 
On soil, viaducts, arches, or tunnels. Engines. Employment of the 
railroad for the transport of travellers, merchandise, or for manufac¬ 
tures and metals. Influence of each of these roads over military 
operations (subject of § IY. of the Memoire). Railways in project. 

Navigation. — Details on each of the practicable rivers: limits and 
extent of the navigable or floatable parts; ports or landings ; impedi¬ 
ments or accidents of the ground which hinder navigation. Works of 
art for keeping up the navigation: dykes, sluices, locks, cuttings, 
weirs, &c. ; cleansing, repairs, &c.; annual duration of the time of 
rest. 

Number, dimension, and draught of water of the boats ; burden in 
tons of the boats navigating by sails, steam, or by being towed ; valua¬ 
tion of the annual transport of travellers, provisions, agricultural and 
industrial, native or foreign merchandise. 

Canals. —Details about every canal passing through the ground 
reconnoitred ; name and ends of the canal; if with points of division; 
lateral to a river, or joining two navigable ways; of great or little 
navigation; length, destination, and importance of the canal; chief 
towns it passes through; breadth at the level of water; depth ; nature 
of the country it passes through; rivers or other waters which feed it; 
works of art for the canal, dykes, sluices, locks, &c.; distance between 
the sluices or locks; height of the fall at the locks. 

Boats , and amount of navigation, as for rivers. 

Maritime Navigation. —In ports, establishments of the royal navy, 
ships of war or belonging to the State. Number and tonnage of 
merchant vessels, of vessels that sail in and out annually. Number of 
sailors ; seamen attached to the colonial or distant trade, to the coasting 
and fishing trades. 

Means of passing Rivers and Canals. —General considerations on the 
points of passage. Existing bridges; their situation, length and 
breadth, their destination; their construction in stone, iron, wood, &c. 
Suspension-bridges of one or more arches ; for carriages or foot 
passengers only; tolls. Drawbridges; lifting or turning bridges; small 
and foot bridges. State of repairs; means of repairing which the 
country affords. How to destroy the bridges. 


120 


A PRACTICAL COURSE OF MILITARY SURVEYING. 


Terry boats, flying bridges. Time necessary for crossing. Number 
of men, horses, and waggons, that they can transport. 

Fords, permanent or moving; their direction, perpendicular or 
oblique to the stream; quality of their bottom, rock, gravel, fixed or 
moving sand; their length and breadth; if they are fit for the passage 
of artillery, cavalry, or only infantry; means of rendering a ford im¬ 
passable. 

Convenient sites for military bridges, pontoons, boats, easels, &c.; 
length which those bridges would have ; facility of approach; passage 
on ice. 

Telegraphic Lines .—Aerial and electric telegraphs. Direction of the 
line. Principal towns where the wires end. Telegraph stations exist¬ 
ing on the ground reconnoitred. 


§ IV. 

Military Considerations. 

Offensive .—General character of the ground reconnoitred considered 
in a military light; advantages offered for operations by the great 
obstacles, communications, and points of support of which possession 
can be taken. Great Ipies of operation, sketch of the same ; openings 
and masses of resistance. Secondary lines of operation. First and 
second-class strategic points to occupy. General outlines of the works 
of fortification and others to be proposed. On the maritime coasts ; 
advantageous points for landing; tonnage of the vessels that can 
land; difficulty of approaching the coasts through winds, tides, &c. 

Defensive .—Extent of the frontier in length and depth; general 
disposition of the ground; great undulations; openings; masses of 
resistance ; lines of defence; protection to be derived from them; lines 
of operations by which they are intersected; strength of the chief 
base of operations, owing to the nature of the ground or to fortified 
points. Points of support for defensive operations. Communications 
(besides the great strategic lines already spoken of) perpendicular or 
oblique to the frontier that are more or less practicable; how to defend 
them. Probable direction of the attacks of the enemy ; of an 


MILITARY SKETCHING. 


121 


invasion. Means of resistance to oppose him, or system of defence 
proposed in the Memoire, according to the configuration of the ground, 
the communications, the defensive resources existing, and the m ili tary 
operations which the ground would allow of. 

In countries difficult of access, mountainous, or covered with 
forests, thickets, or defiles; advantages of their organizing a guerilla 
warfare. Facilities for divers kinds of ambuscade; points of concentra¬ 
tion, rallying-points. Resources of all kind (men, provisions, means of 
transport) to he drawn from the country and the inhabitants for this 
kind of war. 

Near the coasts; maritime attacks to which they are exposed; 
points of landing to watch; system of defence to propose. 

For the interior of the territory; lines of defence in the rear of the 
former; protection they would offer against the probable march of the 
invasion. Additional means of defence. Masses of resistance to be 
turned into account in the defence ; works they would require. 
Defensive points to organize. Points of concentration of the movable 
forces, of the reserves. Decisive points of the theatre of operations. 

Positions .—Positions for a corps d'arm'ee, a division, a detachment 
more or less considerable, covered by natural obstacles or to be en¬ 
trenched. Fields of battle, site for fortresses, entrenched camps, divers 
posts, &c. Details on the positions which the ground encloses, their 
action on the general defence ; distance to the neighbouring fortresses; 
extent of the front, depth; obstacles covering the flanks and front; 
communications and lines of retreat more or less practicable; troops of 
all arms necessary to the defence of each position; safe site for the 
parks; advantage to be derived from cities, villages, castles, churches, 
cemeteries, for defence or shelter; places from which provisions, forage, 
water, and wood, could be drawn. 

For a fortified or a maritime town: full information respecting the 
particular statistics, and application to this place of the above considera¬ 
tions ; advantages or inconveniences of the disposition and construction 
of the works; flanking fire; defilade; strength and capacity of those 
works; their state of repair; front or fronts of attack; description of 
the environs, and statement of the difficulties for an enemy who under¬ 
takes the siege. For maritime places : if the naval establishments are 


122 


A PRACTICAL COURSE OF MILITARY SURVEYING. 


exposed to the effects of a bombardment, or of a fire from steamers or 
rockets; means of preserving them from the effects. 

* V. 

History. 

General History .—Statement of the principal political events that 
have taken place in the country where the ground reconnoitred is 
situated. Origin of the remarkable cities or of the actual population. 
Changes of governments the country has undergone; dominions 
under which it has passed. Great disasters that befell it. Celebrated 
politicians, or military men who influenced the state of the country. 

ArcJioeoloyy .—Remaining monuments of the various epochs, Greek, 
Roman, Christian, &c. Each epoch divided into three classes—Re¬ 
ligious monuments, military monuments, civil monuments. 

Cities or villages, strongholds, castles, ancient camps, temples, &c. ; 
their position, description, vestiges that remain of them. Authorities 
from which the description is taken, historians, drawings, traditions of 
the country, &c. 

Roman ways passing over the ground reconnoitred; lines which 
they follow; where they lead to; their ramifications. Vestiges that 
remain of them. Nature of their materials. 

Documents and historical materials existing in the museums and 
the public or private libraries. Printed works, manuscripts, drawings, 
engravings, and sculptures, that are not generally known. 

Military Events .—Summary of the remarkable military events of 
which the ground has been the theatre, such as battles, combats, 
sieges, &c. Circumstances which historians generally known should 
have passed over, or which lack exactitude. Sources from which the 
information has been extracted. 


APPENDIX. 


On the Representation of Ground. 

During the preparation of this wort, Colonel Scott, R.E., the Examiner in 
Military Drawing, delivered a lecture at Chatham on the representation of 
ground, and in order to remedy the evil alluded to in paragraph 25, and secure 
uniformity of expression from different draughtsmen, he proposed a system very 
likely to be introduced both at Woolwich and Sandhurst. Assuming that the 
horizontal style is preferable to the vertical. Colonel Scott propounds his method 
as follows:— 

“ To convey the idea of relief, it is, of course, necessary to impress on the 
mind of the observer that the points of the drawing, at which he is looking, 
represent points at different levels. 

“ It will seem to him a very natural arrangement that for any assumed unit 
of vertical distance between two points on a slope, whatever its inclination, the 
horizontal space between them should receive a certain fixed proportion of 
shade. 

“ He will also readily admit the idea—the whole plan of the ground being 
covered with the projections of level lines running round the hills, at the assumed 
vertical unit apart—that the shade is diffused over the wide bases of the gentler 
slopes, and concentrated on the narrower bases of the steep inclines, corre¬ 
sponding to such unit. 

“ It will not appear a very forced arrangement if he is told that he is to 
suppose the shading to be laid on in lines at sensible distances apart, in the 
direction of the projections of imaginary level lines running round the hill, 
sometimes in numerous fine lines, and sometimes in what may be considered 
groups of fine lines drawn touching each other, so as to form one or more 
thicker ones, according to the slope of the ground. 

“ He will, indeed, almost anticipate the last idea, for whatever the reason, the 
eye readily enables him to conceive that the thicker lines represent the steeper 
slopes, and that so vividly, that it would be very difficult to dispel the idea when 
once formed. This is fortunate for the success of such hill shading as I am 
advocating, for since a considerable number of lines are required to express the 
minor undulations of gentle slopes falling between two contours, and it would 
be impossible to draw the same number, per vertical unit, on the projections of 



124 


APPENDIX. 


steep slopes, there is nothing left to us but to run the lines together for such 
slopes, either indiscriminately, or so as to form thicker lines with intervals 
between them. Now, it cannot be doubted that the most pleasing and easiest 
way of arranging them will be in lines having a thickness proportioned to the 
increasing slope, the intervals between them being gradually diminished. 

“ This interchangeability of number and thickness in the lines employed to 
produce relief being granted, we may, without doing further violence to the 
observer’s powers of imagination, arrange the scale of their change so as best 
to suit our requirements. 

“ A slight variation is made in the thickness of the lines for the steeper 
slopes according to the scale of the plan, for the obvious reason that the detail of 
a plan on a small scale will not bear so forcible a shading as can be applied, 
without destroying the legibility of the detail, on a large scale. 

“ The scale employed in assisting the draughtsman to estimate the number 
and thickness of strokes per unit for scales of 2 ^wo, s oVcr 
and tows', is shown in the diagram, and little need 
be said in explanation of its use. The draughtsman 
must, of course, take care not to give his plan a ridgy 
appearance, by a servile adhesion to the equi-distance 
of the lines on the scale, when the form of the ground 
requires that the space between the strokes and their 
force should be varied; and he must also, between two 
diverging contours, be careful to change the number 
of his strokes, without producing a harsh effect. The 
dotted lines should be penned in as the shading strokes 
are executed, or they will stand out too harshly. 

“ Nothing need be said either, beyond the infor¬ 
mation given in the following tables, of the system on 
which the number and thickness of these lines have 
been graduated. The object has been simply to make 
the weakness inherent in the means of representing 
relief least felt in the representation of those slopes 
which are of most importance to the tactical move¬ 
ments of armies. 

“ It may be objected—and I know it will be ob¬ 
jected—to the general employment of such a scale for 
giving relief, that it requires too much care and attention to be of service in 



for scales -sAnr) vo’ooj rjrew* 


* In columns 1 and 6 are given the number and thickness of the strokes to be used per vertical 
unit for the slopes named below them, reckoning from axis to axis of the upper and lower strokes in 
each case. In 2 and 5 are given the horizontal distances at which the contours for the said slopes are 
to be shown in dots. In 3 and 6 are given the scale of shade that results from the above arrangement 
for the slopes named. In 4 the spaces a.... a are to be cut out in using the scale, so that column 3 
may be applied to the sketch sheet. 




























































































APPENDIX. 


125 


ordinary field sketching; but to my mind, it hardly needs proof that if draughts¬ 
men are educated to draw with reference to one scale, their early progress will 
not be retarded; and that when obliged to make rapid sketches, their work 
will more nearly approximate to one universal language than if they worked, 
each in his own fashion. A schoolboy is not retarded in his progress in writing 
by the copy-slips put before him; and whereas, if he is, as he grows older, free 
to depart from the forms of letters he was taught, he soon runs into an illegible 
scrawl which becomes worse and worse with practice; he will, if he adopts the 
profession of a clerk—whilst he loses little or nothing in celerity—always 
form his letters, however rapidly he writes, after the perfect type he was first 
taught. 

“ The scale for shading plans with the pen given in the following tables has 
been drawn up in accordance with these views, and will not be found materially 
to differ from that which a good draughtsman, in the horizontal style, employs in 
hill shading. 


Table, showing the Number of Strokes required for different Slopes. 


1 

2 

3 

4 

Number of strokes 
required per vertical 
unit tor the 
scale employed.* 

Approximate slopes 
for which the 
number of strokes, 
shown in column 1, 
are to be employed. 

Approximate angle 
of inclination of the 
slope shown in 
column 2. 

KEMAKKS. 

l 

1. 

o 

45 

The slopes given in column 

2 

i 

26^ 

2 are thus obtained: com- 


2 


mencing with the slope the 

3 

1 

3 

1—i 

oc 

tO|H- 

denominators of the fractions 

A 

1 

11 1 

representing the other slopes 

*± 

s 

11 4 

are the approximate numbers 

5 

1 

T 

81 

derived from the empirical 
formula:— 

6 

1 

TT7 

5f 

Denominator = 1 '5 +1 ( - 5) 

7 

1 

TT 

4 

„ = 1'5 2 + 2 (-5) 

8 

1 

2 3 

„ = 1-5 3 + 3 (-5) 

TiT 


„ = 1-5 4 + 4(5) 

9 

1 

TO 

2 

v . 

10 

1 

TO 


„ = l‘5 n + n(-5) 


The vertical unit here referred to is the same as the vertical distances at which the chain dotted 
contours are to be shown below 5°. (See next Table.) 











126 


APPENDIX. 


Table, showing the distances at which dotted contour lines are to be shown on 
various scales, and for different slopes; and also^the thickness and number 
of the lines to be used in expressing the greatest and least slopes :— 


1 

2 

3 

4 

5 

6 


Vertical distances in feet at which chain-dotted 
contours are to be shown. 


Minimum 



est number of strokes 

ployed on the gentlest 

expressed, including 

;ed contour line. 

1 

For manoeuvring 
slopes. 

For slopes 
which can 
be as¬ 
cended 
singly. 

For slopes 
which 
may be 
climbed. 

Maximum 
for 45°. 

for least 
incli¬ 
nation 
expressed. 

Least inclination 
expressed. 

O 

© 

73 

© 

GQ 

Below 5°. 

From 

5° to 10°. 

From 
10° to 15°. 

From 1 From 
15° to 30°. 30° to 45°. 

| 

Thickness of lines 
to be used for the 
different slopes in 
fractions of an inch. 

Fractions 
repre¬ 
senting 
slopes. 

Angles of 
slopes 
with 
horizon. 

-w g 43 
® S B o 

£ 1) ©T3 
&-£> ® 

EH 

1 

2 5 0 0 

5 

10 

15 

25 

50 

1 

■go- 

rw 

1 

4 0 

o 

n 

10 

1 

10 

20 

30 

50 

100 

1 

4o 

1 

1 

415* 

n 

10 

Sooo 

40 o 


1 

20 

40 

60 

100 

200 

i 

44 

1 

1 

44 

u 

10 

1 0 0 0 0 

6 0 0 

4 

1 

40 

80 

120 

200 

400 

1 

1 

1 

BIT. 

2 

9 

20000 

7 0 

RHO 



1 

4 0 0 0 0 

80 

160 

240 

400 

800 

1 

*§4 

1 

6 4 0 

1 

4T 

2f 

8 

1 

160 

320 

480 

800 

1600 

i 

1 

1 

4 

7 

Tffooo 

10 0 

7 0 0 

T4 




The slopes in column 2 have reference to the following table. 


1 .—Gradations admitting of Manoeuvres. 

(According to Lehman.) 

5° 

10° 

15° 

Infantry 

Infantry. 

Infantry 

may move with order, and 

Its close movements be- 

cannot move any consider- 

has, down hill, the most 

come more difficult. 

able distance with order; 

effectual fire and charge. 


their fire up hill without 
effect. 

Cavalry 

Cavalry 

Cavalry 

may also move with order, 

can only canter down hill, 

may still trot up, and 

and has, up hill, its most 

the charge possible only 

walk down hill. 

effectual shock. 

up hill. 


Artillery 

Artillery 

Artillery 

has a more effectual fire 

moves with difficulty, its 

moves with great difficulty, 

down than up hill. 

effectual and constant fire 
ceases. 

its fire totally ceases. 







































APPENDIX. 


127 


2.— Gradations which may he ascended and descended singly. 

20 ° 

25° 

O 

O 

CO 

Infantry 

cannot move in order, and 
can fire only singly with 
effect. 

Cavalry 

may still ascend at a walk, 
and descend without order, 
and that only obliquely. 

Infantry. 

Light infantry as before. 

Cavalry. 

Light cavalry may ascend 
one by one obliquely, and 
descend in the same way, 
but with great difficulty. 

Infantry. 

Chasseurs and Riflemen, 
as Light Infantry before. 

Cavalry. 

Hussars may ascend as 
above, but with great 
difficulty, and when the 
slope is of soft earth. 

3.— Gradations which may he climbed up. 

3 5° 

40° 

45° 

Chasseurs and Riflemen 
may ascend with difficulty 
one by one. 

Chasseurs and Riflemen, 
without baggage, may as¬ 
cend with help of their 
hands. 

Chasseurs and Riflemen 
accustomed to hilly coun¬ 
try may ascend as above, 
but with danger of falling. 


“ The greatest thickness for the lines in column 3 has been obtained by 
micrometric measurement from good specimens of hill sketching. The thickness 
for intermediate slopes will be obtained by dividing the greatest thickness by 
the number of strokes corresponding to each slope given in the preceding table. 
It is not, however, supposed, that in practice, a draughtsman can do more than 
approximate to these thicknesses. 

“ The least thickness in column 4 is obtained by dividing the thicknesses in 
column 3 by the numbers given in column 6; they agree with the micrometric 
measurements of the fine lines in good specimens of drawing. 

“ Column 5 has been determined with reference to the slopes which appear 
to admit of being shown on the scales indicated in column 1, and from existing 
good drawings. 

“ The numbers in column 6 follow from the slopes in column 5, and are 
derived from the preceding table. 

“ The scale also as regards the efficient draughtsman is intended to be a remem¬ 
brancer, merely, of the gradations of shade which he, and those who work with 
him, are to employ; and, though it undoubtedly limits his power to please us, 
at the expense of truthfulness, it still leaves him plenty of scope for exhibiting 
his artistic talents. It approximates, indeed, as nearly as possible to those which 
I have found to be used by our most effective hill sketchers. 

“ It is to be remembered that a defect in shading on the principle recom¬ 
mended only interferes with the proper expression of the pictorial part of the 













128 


APPENDIX. 


work; it cannot vitiate the general form of the hill which the contours trace 
out; and these, by the definite language which they speak, check at once very 
serious inaccuracies. 

“ This, then, is the system which I have to propose ; it makes no pretension 
to originality of conception, or to he supported by any learned argument on 
mathematical or natural representation. The chief aim has been to adopt the 
simplest forms of conventionality consistent with that degree of naturalness of 
representation which is necessary to impart the idea of relief, without strain on 
the imagination and memory of the observer; consistent also with giving aid to 
the sketcher in his labours, and enabling him best to delineate those gradations 
of slope which it is of most importance to a general, in command of an army 
in the field, to read with some degree of accuracy.” 

This method has for object to secure uniformity in the representation of the 
same ground by different draughtsmen, and to combine accuracy with pictorial 
effect. The accuracy is secured by the chain-dotted contours, and the effect by 
a diapason of shade, giving a tint proportional to the inclination. Plate 40 
has been drawn by Major Petley according to the diapason, but the chain- 
dotted contours have been omitted. 




INDEX 


Aerography, 114. 

Agriculture, 116. 

Archaeology, 122. 

Bardin (Professor), 18. 

Base, 28. 

Basin, 19. 

Basins, 111. 

Bearings, 49. 

Bisecting an angle, 41. 

Box sextant, 69. 

Brushing with Indian ink, 18. 

Buildings, 9. 

Canals, 119, 

Canvas, 26. 

Canvas of levelling, 97. 

Cattle, 117. 

Chaining, 30. . 

Clinometer, 80. 

Clinometer Trinquier, 87. 

Col, 19. 

Colour, 8. 

Commerce, 118. 

Communications, 118. 

Conditions to he fulfilled by a military survey, 
7, 10. 

Construction of scales, 31. 

Contours, 10. 

Conventional signs, 4, 7. 

Co-ordinates, 94. 

Copy of plans, 23. 

Counterforts, 20. 

Coup d’oeil militaire, 2. 

Crest, 19. 

Crimean survey, 14. 

Cross staff, 75. 

Dales, 21. 

Declination, 56. 

Defensive, 120. 

Defiles, 20. 

Diapasons, 16. 

Distances, 30. 

Distances reduced to the horizon, 35, 89. 
Echelle rapporteur, 57. 


English system, 13. 

Equidistance, 12, 

Error in reading, 5. 

Features of the ground, 19. 

Filling in details, 27, 95, 104. 

Finding the distance between two points, 38, 
41, 75, 103. 

Finding the direction of the capital of a bas¬ 
tion, 43, 55. 

Finding the height of a building, 43. 

Finding one’s place in a survey, 54, 65. 

Form of triangles, 28. 

French diapason, 16. 

„ system, 15. 

Gardens, 9. 

General configuration of the ground, 111. 

„ history, 122. 

Geodesy, 3. 

Geography, 3. 

Geometrical representations, 11. 

German systems, 13, 17, 18. 

Guessing distances, 31. 

Hills, 20. 

History, 122. 

Horizontal style, 13. 

Houses, 116. 

Hydrography, 112. 

Industry, 117. 

Irregular survey, 2. 

Itineraires, 109. 

Jackson (Colonel), 14. 

Lakes, 9. 

Land communications, 118. 

Language, 114. 

Lehman’s diapason, 17. 

Levelling, 3, 80. 

Levelling with plane table, 86. 

Light, 8. 

Limits of topography, 3. 

Magnetic azimuth, 49. 

K 







130 


INDEX. 


Major Fevre’s table, 66. 

„ „ scale, 68. 

Making an angle equal to a given angle, 39. 
March of a survey, 91. 

Maritime navigation, 119. 

Materials, 116. 

Maximum dimensions of triangles, 29. 

Means of passing rivers, 119. 

Memoire, 102. 

Method of intersection, 54. 

Meridian line, 93. 

Military considerations, 120. 

„ events, 122. 

„ positions, 121. 

„ signs, 8. 

„ sketch, 2. 

„ sketching, 103. 

„ surveying, 1, 91. 

Militia, 115. 

Minute, 8. 

Models, 1. 

Nature of the soil, 113. 

Navigation, 119. 

Oblique light, 118. 

Offensive, 120. 

Order to follow in copying plans, 24. 
Orography, 111. 

Pacing, 30. 

Perspective, 18. 

Petley (Major), 14. 

Physical description, 111. 

Plan, 2. 

Plane table, 59. 

Planimetry, 3. 

Plotting, 29. 

Polar star, 94. 

Political divisions, 114. 

Ponds, 9. 

Population, 114. 

Preliminary canvas, 91. 

Prismatic compass, 49. 

Producing a direction beyond an obstacle, 40, 

101 . 

Profiles, 11. 

Protractors, 51. 

Public buildings, 115. 

„ revenue, 118. 

Railroads, 9, 118. 

Ravine, 22. 

Reconnoitring, 2, 110. 

Reduction of plans, 23. 

Religion, 115. 

Representation of the ground, 10. 


Resources for lodging troops, 116. 

Richard’s (Captain), 14. 

Riding, 30. 

Rivers, 9. 

Roads, 9, 118. 

Scales, 4. 

,, usually employed, 6. 

„ for foreign plans, 34. 

„ for walking, trotting, or galloping, 34. 
Sea-coasts, 113. 

Selection of a scale, 4. 

Shading, 13. 

Sight-rulers, 61. 

Sketching details, 104. 

„ the features of the ground, 98. 

Stadia, 31. 

Statistics, 114. 

Surveying with a chain, 46. 

,, „ plane table, 61. 

„ „ prismatic compass, 54. 

„ a polygon, 78. 

,, a road, 55. 

„ a river, 78. 

„ a village, 96. 

Survey at sight, 106. 

„ by memory, 109. 

Table-land, 19. 

Table of tangents, 82. 

Taking the back angle, 55. 

Telegraphic lines, 120. 

Thalweg, 21. 

Three methods of surveying, 27. 
Tithes-commissioners’ signs, 7. 

Topography, 1. 

Topographical drawing, 7. 

Tracing contours, 99. 

„ a direction on the ground, 36. 

„ a parallel to a given line, 39, 64, 102, 
„ a perpendicular „ 37, 74, 76. 

Traversing, 55. 

Trees, 9. 

Triangulation, 26. 

Trinquier, 57. 

Valuation of angles, 107. 

Valley, 21. 

Vernier, 70. 

Vertical style, 14. 

Water-level, 83. 

Water-sheds, 19. 

Winkel-ICreutz, 108. 

Woods, 9, 117. 

Yeomanry, 116 






ERRATA 


Page 15, line 7 instead of 

ac = cb 

read 

ac = ab 

18 „ 

1 

99 

margin 

99 

horizon 

18 „ 

3 

JJ 

5 to 6 

99 

5 to 5 

24 „ 

6 

99 

square 

99 

squares 

24 „ 

11 

J) 

contour 

99 

contours 

25 „ 

1 

JJ 

AC': AB' 

99 

AC : AB 

28 „ 

8 

99 

BAB 

99 

BAG 

32 „ 

6 

99 

perpendicular 

99 

perpendiculars 

44 „ 

2 from bottom 

99 

On the plan 

99 

On the plan construct 

47 „ 

2 

99 

X 

99 

X 

Reference to 79, 80, &c., to 87, should be altered to 78, 

79, &c., 

to 86 

Page 63, line 3 instead of 

a b 

read 

b x 

63 „ 

5 from bottom 

99 

plan 

99 

plane 

64 „ 

2 

99 

z / x . 

99 

a,x. 

64 „ 

11 

99 

in line the edge 

99 

in line; the edge 

71 „ 

7 

99 

(n-1), D 

99 

(n-l)D 

71 „ 

7 from bottom 

99 

12°-9' 

99 

12° 9' 

72 „ 

2 

„ eAceed 

or fall short of 360 

O 

99 

exceed 360° 

83 „ 

4 from bottom 

99 

ad b c 

99 

a d, b c 

96 „ 

2 

99 

outline 

99 

outlines 

100 „ 

5 from bottom 

99 

(Euclid, p. lvi.) 

99 

(Euclid, lib. lvi.) 

101 „ 

2 from bottom 

99 

the less 

99 

the least 










PLATE I 


CONVENTIONAL SIGNS. 

FOR THE SCALE OF 6 INCHES TO / M : !. E. 


Common/1. and. 




Wood/ Zand. 







Coppice/ Wood/. 


■ ' .« to* ARk M » A 


r/- JL'"*«'«> 

5?&* JL-- 



^ •VarT'2 ■ 


ZfeaJdi/, Fern/. 


~#*S. ’»*•* — 'CjN- ««%v. 

^- ++zz- **• *«*• ~*“- 

><*"»£.-- »™* l 'v. .*»*52is. .A '^Sfc ** 

*-•> — 


,«\witt.. a . . rff>«'*5s *~--'"22S 

-V>__ «*V «v«s. 


Zlarctatbons. 


Coppice'/ -with Timber 


Rabbit/ Warrens and 
SaTui/JfMs. 


Tanks. 


*.T ,*A>- .(&•*•:*.&- 

> . . • P ',-• 

■ .-W^" '•'•■ •' • ■ 

CZ0 : d0T : : <{0r~ 

Arf; nirZWWlF'' 

MxorF 


| ci?.-# & 

TA crt=a '.-»• T 'F^r-' Z » 

i rf. 4 4 4;^ ** 

*•/. ... -~Ti» , T". v'.“ / A A*'”' o 

•^L (« ^ ; A • • <■ 

4t-a i* 

— r ^ <>. n cpi C(<.C^ ft 


• n <i<- 1 

^4*4 n *£ 


‘ **> c*-*, ’-K 1 


<3$.>48<# 

:<*.&>$■ IT fj'ta. M'F_ 

%-i Cb>'^ $■'’ ij It 

* &\vf.' <*v, VA «-> ®= li *•• >''■ 

A*- '4 .v j.£> i, 


r > ; J^' ■c&'t-x. 


-r. '?.-' &:aiC P r 1 ‘‘ v • 

& "Jfc 

'■C • • ’^Z. fd^rCC. cT ***** ' 

' C f .... (5. (t t ^ 

A. 

IK- *i >' 

i. at. G-.r < 7?; 


^ #; e » « 


low 






Cultivated/ Fields. 


Orchards. 


Cardens. 


Vineyards. 


Aay Vie. colour A’U^.tToTovi'iv 


_ A// u, ‘, i.‘Oil,, i! , 'if-' ^ 

mam$m 


.s^, ^ an 

^ ^ ^ ^ 
an ^ ^ 

# a? 1 — ~ 




rrr-rr^T 

< { 1 L < 

» 1 < / 4 « 


< t t f 

< ( 
t « 


< 


Meadows. 


Fop Grounds. 


< /// m _ L j_ ; 

M<" 7 < 1 


Sand k Mud barks. 


♦ M < { v 

* (<<•*/ 

A 


iRooJas. 


S 



/f AA,^. AAAAAA 

A AAAAAAAAA 
/K A A A A AA A AA A 

JJ 

// 

S . 

FiecLch Gr A 

Tenter Gr- 


11 
Ml 
11 
II 
11 
M 
ill 
ll| 
III 
III 

‘ * * * * * 

^0 


„S*#? 

://" v jsfe 

A# 






<w». 




T;? J 



Zand subject/ to 
innruZcUto/is. 


cum. 


Oder Zeds 


Ithdrouned -Marshes 



it II 4t l>, ^ 4 «*■ 

4 4 j&iiL 4^ 

■eifc Affc. j4l. A4 ^4 i^6 

j^L .i£ M ^ i. 4i ^ 
Ail Jja. & xfc iH 
ti. ^ M, Mr M 



-Marshy Ground. 


•Ic3, iilh ' 


Xionrlon.PiiblisTi^T .Tune 1864 * TayAtchlay &C? 106 , G-V Russell W.C. 

























































'PLATE II. 


CONVENTIONAL SIGNS. 

FOR THE SCALE OF 3 INCHES TO / MILE 


Common/ Zand 


Wood/ Zand/. 


Coppice/ Woods. 


IfeaJZ, Term. 


•«** **Si8k 

■** ■ 
44 * ■* 

• ' t /t *. • 

fi'<* Hr f*' -. .% . .«*•: 


..< ' b 

' A. 




4- 


■% 


755- 


r/v _ /~ S?Cp-' ' /~ 

-***. J °> ''JU. 

V u 4 ^.' -^T- - <V 

T ? (t % 

' •>, ff ' 

-J?V - «c^~ Jk 

■■' -p (I. /^/f L c, ' r 

\ it:,, jt 


Ue^r jP' 

;1 <4, 7T. " 


^ 1 u. 


«T£_ "tt. •- 
-■ - .,** . rft- 


„„ «*!E ^T.:- •*: » , ''i »«■ «n- 

>' , 'st; -«* "".s. "'"'At- •<& •VSi-t- 
..,.'5cr »«*• . e 


..At ■••!: 


JPLanta/dons. 


Coppice/ with/Timber. 


Eabbit WarrensISaruikdls 


darks. 


£-r»' , 


, 4 if 


. '±%%‘hs 


(t o- .'■ ‘ - 


T. '.T^ v iv a zurr. G. 

4 u l 4 £& ^ 4 <4 '■$ £ fct 4 ^ ( ’e *a* ^ 

«'■ 1 . (v : •^' (r 

^ 44 6 £ A4 4 *1 « J M 4 ■‘■fc «*£ 

, u , /> (c/?|^rr, ' v , h. 

4lU*U«4 * •<*4i 44«***^ 

a" 4 l‘« ^ 

hi Wi \ 

4AL«sfrte-. 4:. 4«+ * 


'iL 1 :< *"‘£;^ 

A'r. \/-t ' , - ;xr ... .r 


JTAfPi 


K. /; 


a (i r c$, 
Cr 


Jk 


jj% ;^Af 


ZZ'tZZZ 

■ ■ ■ k-/r »J{t-jur- 

h/^o f c vf/ 


a. r, ~-'M 

1 rP>- 



L -i* ; :<i ZZ <4 •* 4 

<* «*:: "t ej^'V 44 4 r 

! .. .4 ^ ■> '•" •' 


m 




...■rt .'4 


-t 


Culta/outed/Titlds. 


Orckiards. 


Gardens. 


Vineyards. 


May he- coloured/ light brawn 

t 

Trrrr'7?CiTppn-f~~-~jr-g 

ZMtZ0dttwZvTFL 

Tin iTl!!! iGGpoiT 
Meadows. 



'* 4 .IS | ‘t <* 'i 

4 ■!« if 14 -4 4 

*> ij 4 \ SI ,8f (. 

"* "i 

TV* * * a 

,. li\'-i "= “4 / ••» '<i 

a ",* »*\« ^ 1 « 2 •* 

.-% ** ^ 4 {4 »fe 


- 



Grounds. 

t\ h\ A* 'k. 

****** «.***»■ 


Meaoh/ Gr. 


Tenter Gr. 



Zands subject/ to 
Irmndatiom. 


Cliffs. 


Ozier beds. 


Zfndrained Marshes. 



VineenL Brooks.lith. London. 


London: Pubiislied June 18 64, "by Alchley (5c C? 106, Gb Russell W. C. 







































































PLATE LI . 


CONVENTIONAL SICNS. 



LonJon: Bibliskecl June 1864 "byAtohley &C? 106,'ll Russell St- W.C. 







































































































































































































PLATE IY. 


CON V ENTIONAL SIGNS. 



Scale of 6in.tolm. 

Scale of 3 ia.to 1 m. 

Tarthen/Tenses 






Walls 



Foul Fences, Toutings 

Hedges 

Hedges with/Trees 

.N 



_ 



ZwuuJtilnb 

@ 

@ 

Churches 

♦ 

4 

Houses 

' «sa 

MM 

and 



Farms 

| - . 

sresa |® IWi 1 

E2 


f may be coloured/ Fed.) 

(do.) 

Smithies 


A 

Stone/ Windmills 


%: 

Woodero do. 


& 

Watermills 



From Works 

A A: 

AA 

Glass do. 

0‘ o 

* a 

Tig hi/ Houses 

i 

1 

Telegraphs 

i 

i J 

lies cary 

? 


Copper 

? 


Teocd 



Silver 

> 

y 

Gold 

o 

Iron/ 

jf 


Tin/ 

21 


Coal/ 

\ 

* 



Vincent Brooks, litk.Iion.dnn. 


London. PabliskecL tTane 1864* kjT Atdhlery Sc G? 106, G*‘ Rasa ell V\. C 






































PLATE Y. 






London: Pablisliefl June 1864 "by Atchley & C° 106, G-l Has a ell St- W.C. 





































































SECTIONS ( SEE PLATE V.) 

« 

ON BASE LINES 1500 FT ABOVE THE SEA LEVEL. 


PLATE VI 



Vincent Brooke, litk. London 


London.PabHslied June 1864 By AieHLey &.C° 106, GV EuasedL S + W.O. 


SCALE OF 3 INCHES TO / MILE. 
































































































































































































































































































\ 






'• 




* 
















































I 

















* 
























\ 




p 















SECTION ON AB. 


PLATE VII. 





































































































































PLATE VIII 



Jjonrloti "Pij-bKsliftcl ‘Tun^ ^ 


IwAtchl^y &-CV 106, G* Bussell St W.v! 






















































































































































■» . ' 











- 



















4 
















• 







9 . 

V* 






























, 

' 













, 






' 







PLATE IX . 


A 



London PoblisM- June 1864 lyAtchley & C° 106, GV Russell S? W.C. 


















































































, 


































































































* . - 




.. 


















. 








. 






































« 







































M 
















■ . * 




* 































■ 






























PLATE X 



Lot Imr.RibhsM .Time JB o4 Iry At’hlev \.r* 1Of'. K *■**■>■ ■" 
































MAJOR PETLEYS SERIES. 


PLATE 



ioncicm:Published June 1864 by Atahley 106,&V Fuseli SI W.$. 

























































































’ 









y 


K 





r 







* 


» 






■t 


4 















- 







% 






* 






X 











> 



I 


\ 





PLATE XII. ■ ' 


MAJOR PETLEY’S SERIES. 



Vincent Brorxke. iitii. London 


London-.JPubHahed. June B64Atohley K6,GV EuasdU P W.C 








* 

. 


- V 













- 














































































* 












• - 

























> • 

































' A 


r* 















' ♦ 

... 


























‘ 



* 



























































MAJOR PETLEY’S *SERI ES. 


PLATE XIII. 



Vincent Bro oks, lith. London. 


L rmrl nn: Pabliailed June 1864 Ly AtcLlery- Sc C° 106, GV Russell W, C. 













































• 

. 






































- 
































• 






. 

























, 






































• J 




































































PLATE XIV. 


MAJOR PETLEY’S SERIES. 






V $Y> V >'' 




Vm.ppn r. "BtooT»b ilrth li onion. 


London PubHslied .Tone 1864 "by Alchley 8c C? 106, G*- Russell S* W. C. 









\ 






















I 













* 









I 















V 






/ 







- 


- 






* 











MAJOR PETLEYS SERIES 


PLATE XV 



Violent TJpooLs.lith. Londo-n 


London : PiibKslied .Tune 18 64 ,"by AfceKLey 8c. C? 10 6, GV'Rua sell S t W. C . 











































SI 















































»- 








































t 


















MAJOR PETLEYS SERIES. 



Vincent Brooks, lith. London 


LoncWPubhshea .Tune 1R64 Try Atekley 5c C° 106.GV Russell b* W C. 


















PLATE XVI .(tv) 


MAJOR PETLEYS SERIES. 



Vineexi-t"Broo"ke, lith. London 


London:Publislied June 1864.Try Atehley AC? 106,«■ Russell S* W.C 






















PLATE XVII. 


A MIL I T A RY S K ET CH 

BY MAJOR PET LEY. 


LAI§*• 

// 4' 



Vincent Br o oka ,lith Lon cion 


London.PiibTiffTiecL June IB64 "by Atchlev Sc C? 106, G* Russell St "W. C. 




















































































f 
















V 




























- 






• - 


















. 




























- 











































' 

■ 


■r . 



















'•! 





























/ 





<• * 






• 





• 




























•4 






■ 
























PL ATI 


A MILITARY SKETCH 

BY C A P T * RICHARDS. 



Vinc ent- Brooks,lith..London. 



Lcmaon: RaHisVi .hm*1864. VyAtdOeyJOfi.O* Russell S? W.C. 


XVltl. 





































































































































' 




. 

, 

■ 

. 




























’ 

_ 


-- 


















-J 

* « ‘ 


- t 










* 




























. 









I 












































« 






























. . 


■ 





















1.9 





























PLATE XIX. 



Pu'mI- h- 


Pv Ai- ; hLev Sc CO 106, GV B.u?selL SV W 0 










■ 
















% 






















* 























» 

















» 






















SECTION ON 


PLATE XX . 



Lamlan ftiblislwd. ,Tui» J&64 VrAtoHley & C° 106, 'SV ftasseU S'? W.C. 





















































, 






















































































































' 














. ’ 

r 






- fv 1 




: I 

JI 











>, . .. w 

































- • 
















i" . - , 


















PLATE XXI. 



.London: Published- June 18 64*. "by Atchley 5c C? 106, G*- Hubs ell S'V "W.C. 











































































I 







PLATE XX.; 


* 



*4 


> 










loncLon: RibliskeA JAne 1864. lay Atehley & C° 106, & Russell W.C. 



















































PLATE XXIII 



1930 ff- 


17 30 


1150 


1690 


Scale of 3 inches' io 1 miles. 


London . PublislieA June 1864,"by Atehley AC? 106, GV Russell S* W.C. 


























































































"° ^llllllll[|||ITTnTTTTi ; 


PLATE XXIV. 


FROM THE QUARTERMASTER-GENERAL'S 
SURVEY IN THE CRIMEA. 



Vrru exit. Brooks, iith. London 


SCALE OF 4 INCHES TO / M/LE. 


London.:Published Tone 1864 Try Atchley &.C? 106, GV Russell S fc W.C. 




























SCALE 20,000 


PLATE XXV 


FROM PROFESSOR BARDINS SERIES. 





Vincent Bi'ooka, nth xjOxui.cn. 




/ 


Bondon : jPubHslie^i <lfune 18 64. "by .Atchlev Sc C° 106, I'us sell ST W.C 






























- V 






































t 











* 































SCALE 20,000 


\ 

PL'ATE XXVI. 


FROM PROFESSOR BARDINS SERIES. 



VmcenE Brooke, lith London 


p§gj 

V x 

™p§ 


\ /\\J 

)j 





§p§l 

ml 



London.: -Pulxhslied . June 18 64. "by Atrihley Sc C? 106 ( t \ Rij-sftlL SV WO. 

















































I 






l 








l 






PLATE XXVIL. 



LottHon: PubEshed. .Tune IB 64 /by Atebley «cC? 106, GV Russell &! W.C. 






















































PLATE xxmfa 


s 



















































































































































































































































































































































































































































































PLATE XXVII.fi; 


from wyld’s map of the 

WESTERN PYRENEES. 

(ana lytograph process) 



Vincent ifcoota.i’hoto-Jitho.Icnclan. 


.tuW-RjKliBheA Jan* 1804 “byAtohlev & C? 106, Gfr'Bws Sell S> W 

































PLATE XXVIII. 



I.anilomPabKsW June-1864 TjyAtohley 106,®' Hussell S? W.C 





































































































' 

















































































































- 

















































/ 








































































PLATE XXIX 



Vincent Brooks.lith. liondon 


T.Anion PuHisW June 1864 ~by Atahley & C? Russell 8* W.C. 






































































































PLATE XXX. 




London.. Published Pane 1864 hy Archie v- Sc C ' 106, GV Ruesell ' W. J. 

























































































i 



































J 









■ts "i 


































< 








' 







t- 

















. 









* 




i 






















PLATE XXXI. 





Icmlsii KbKsSiei June 1864 "byAtchley & C? 106, Gt ItasseU St- W.C. 




Viiicent Brocks, lith..London. 

Scale of 6 inches to 1 mile/. 


























































■ 











PLATE XXXII. ■ 



Scale of 3 inches to 1 mile. 



ioo'ff 


mAidimM 


Vincent Bacocika.’lith.. London. 


Smlc of 2 in. to 1 mile 


Sea leoClin.to 1 ni , 



■LotkLoh;P ixblisliei Jane 1864 Sy -Alcli- 0 ■ r Sc C? 106. GMlasselL SI MI C. 

















































































* 







» - 



» • 


























■ 














. 
















. 
















- 










































V \ J 





i 















r - •» • - •, , » •/ 































































Section on AB. 


PLATE XXXIII. 



ITtnci-nt Brooks, lith. London. 


Scale, of 3 inches to 1 mile. 




lonclon: Pttblish.ea Ju.ne.l864',})y Atohley &C? 1D6.G? Russgll S* W.C. 






































PLATE XXXIV. 


PHOTO - L1T H 0 OF THE ENCLISH 
ORDNANCE SURVEY, ( Y0RKSHIRE ) 



% 


London.-.Published June 1864,“by Atehley &C? 106, GV Russell SI W.C. 



























































































V 

■ 


































I 











' 


































































PLATE XXXV. 

PHOTO- LITHO OF THE. 

FRENCH ORDNANCE MAP. 

(PYRENEES) 



Vincent Broc&s,Pho to-Hth-O. London. 

f 

SCALE 80,00 0 


London: RiblishegL June 1864 TojAtchley Sc C? 106, Gt Russell St W C 











































































■sK" 














































































































PLATE XXXVI. 


SKETCH of the RO 

fromMircour to Rurulle 



Vincent B re; ks, lith.. Iioncv j ; 


SCALE OF 3 INCHES TO / MILE. 


London "PabTislled. June 1864 Atdllfly & C° 106, ©■ Russell S? W.C. 






























t- 








. 

























































































































« 








* 













' , 
:* 

















- 

. 










PLATE XXXVII. 



Lanion Published. June 1864* by Atchley 5c C° 106, G-V Russel!. 8T IV. C. 


C* 






















PLATE XXXVIII. 



u. 


B 


Y 


o 


Vincent 13 re -l.s, lith, London. 

UJ 

Directions. 

1. Copy that portion* of this example- whlch-is below the-line'l Y uvpen orpencil/ employing 
cither vertical/ or horizontal strokes to shew the Ibrrru of theground/, or ifyowprefer it, 
use the h rush/for its representation/. 

2. /Draw Sections on the lines A B , C D, & E F , as arcwrately as yow can. 

3. 'IPrint the /title in the- characters used- on- the example. 

4. Give specimens of the manner m- whfch/ycu- would represent woods, marshes, nocks Sc 
-villages on, apian, drawn to a. scale of W 800 or 300 yards to / fnrfu. 


London Pi tblisKed June 1864 "by Atchlsy St C? 106, Gt "Russell St WC. 
























PLATE XXXIX. 



Instructions. 


1. Copy the upper half of thcplan, inpero,penrzl-, or in brushwork; using a horizontal 
or vertical style of kachure as yoic may prefer. 

The dotted lines shew Contour's at 20 feet vertical intervals and wdl be found 
useful/ in making the Sedans. Their suppression in, the copy wrff not be con¬ 
sider erf to detract from, its merit. 

2 . Draw «/ scale for the plan 

3. Draw Sections as accurately as you/can on the/ lines A B , C D , E F. 

4. Represent a, marsh, a/village, cosew becudoJc overhanging cliffs, He co wood, 
suitable for the alove scale. 

5. Tnni the Title neatly iro the characters ga/en in the copy 


Lon-V-n Fubli.-’ln-i .’uno i V-4. by .A ten lev Sc 0? 106. G* Russell 















































* 














































I * 


* 














* 



















*» 





























♦ 































EXAMPLE OF 

ACCORDING TO COLONE 

(the chain-dotted con 
























PLATE XI 


LL SHADING, 

scotts diapason . 

RS ARE NOT-FIGURED) 

































































In One Volume, Octavo, cloth, with Plates, £1. 

THE PRACTICE OF ENGINEERING FIELD WORK, 

APPLIED TO LAND, HYDROGRAPHIC AND HYDRAULIC SURVEYING AND LEVELLING, 

Eor Railways, Canals, Harbours, Towns, Water Supply, Ranging Curves and Centre Lines, Gauging 
Streams, &c. Including the description and use of Surveying and Levelling Instruments, 
and the Practical Application of Trigonometrical Tables. 

Illustrated by numerous Plans and Diagrams. 

By W. DAVIS HASKOLL, Civil Engineer, Author of “Railwat Construction,” &c. 

To remedy deficiencies, and at the same time to supply such numerous practical examples and rules as 
are constantly required in the multifarious operations of English Engineering Surveyors, now engaged in every 
quarter of the globe, and to bring these within the compass of one volume, have been the object of the Author’s 
labours in the work now submitted to the Profession. 

“We hear of ‘French without a Master,’ and Mr. Haskoll’s book might fairly be called ‘Land 
Surveying without a Master,’ its instructions are so full and so clear. It begins at the beginning, and takes 
nothing for granted; and those who master its teachings will find few difficulties in the field they will not be able 
to overcome. In addition to what is shown of its scope by the title, the book includes notes on the description 
and use of surveying and levelling instruments, and the practical application of trigonometrical tables, and is illus¬ 
trated by numerous plans and diagrams. We may safely recommend it.”— Builder. 


MALLEABLE IRON BRIDGES: con¬ 

taining, 1st Series. 

The Britannia Bridge over the Menai Straits. 

The Bridge at St. George’s Landing-stage, Liverpool. 
The Bridge over the River Trent, at Gainsborough. 

These three Bridges, with the details of each, 1 imperial 
folio volume, plates on copper, bound in cloth, and 
text, 4to, price £2 12s. 6d. 

BRICK BRIDGES, SEWERS AND 

CULVERTS. 2nd Series. Each example fully ex¬ 
hibited in working plans and sections; iinpl. folio 
plates, with 4to letterpress, price £1 Us. 6d. 

TIMBER BRIDGES AND VIADUCTS. 

3rd Series. Folio plates, 4to, letterpress, working 
drawings, £1 11s. 6d. 

IRON BRIDGES. 4th Series. Folio 

plates, 4to, letterpress, working drawings, £1 Us. 6d. 

MOVING BRIDGES, IRON, SUSPEN¬ 
SION, and OBLIQUE BRIDGES and VIA¬ 
DUCTS. 5th Series. Folio plates, 4to, letterpress, 
£1 Us. 6d. 

STATIONS, WAREHOUSES, &c. 6th 

Series. With full detailed working drawings, £2 12s. 
6d. By G. D. Dempsey, C.E. 

EXAMPLES OF IRON APPLIED TO 

KAILWAY STKUCTUKES. This work comprises 
illustrations of the application of iron to the construc¬ 
tion of railway and other works. 4to, with detailed 
plates, 10s. 6d. By G. D. Dempsey, C.E. 

THE MACHINERY OF THE NINE¬ 
TEENTH CENTURY. In Six Parts. Complete, 
30s., Impl. folio plates, and 4to text. By G. D. 
Dempsey, C.E. 

EXAMPLES OF IRON ROOFS, of 

various Spans, from 20 to 154 ft., comprising practical 
sections and details of the best examples. Impl. folio 
plates, 4to, letterpress, £1 11s. 6d., 1st Vol. 2nd 
Vol. £1 Us. 6d. By G. D. Dempsey, C.E. 


A NEW PRACTICAL WORK on IRON 

ROOFS. Vol. III., 4to, 10s. 6d., being a Theoreti¬ 
cal and Practical Treatise on the Construction of 
Roofs. Illustrated with numerous Diagrams. By 
Francis Campin, C.E., forming a Supplementary 
Volume to Mr. Dempsey’s large work, Examples of 
Iron Roofs. 

TIMBER ROOFS. Large Folio Detailed 

Plates, and 4to text, £1 Us. 6d. 

A NEW PRACTICAL WORK ON 

MECHANICAL ENGINEERING; with also a 
Chemical Analysis of Iron and its Ores. Fully illus¬ 
trated by 28 plates of Workshop Machinery, Boilers, 
Pumping, Rotative, Marine, Locomotive, Traction, 
and Steam Fire Engines, and 91 Woodcuts. By 
Francis Campin, Engineer. 8vo, cloth, 27s. 

NEW OFFICE BOOK FOR ARCHI¬ 
TECTS, ENGINEERS, &c. With Experiments, by 
G. Rennie, Esq., C.E. 5s. 6d. 

INCITEMENTS TO THE STUDY OF 

THE STEAM ENGINE. 2nd Edition, enlarged. 
By W. Templeton, Engineer. Cloth, 5s. 6d. 

THE OFFICE AND CABIN COM¬ 
PANION. 2nd Edition. By J. Simon Holland, 
Chief Draftsman Steam Branch of the Controller of 
the Navy’s Department. Price 5s. 6d. These Tables 
are ordered to be used by the Admiralty. 

A NEW WORK ON MINING, ENGI¬ 
NEERING, LAND AND RAILWAY SURVEY- 
IN G. Hlustrated with numerous plates and diagrams, 
royal 8vo, cloth, 30s. By H. D. Hoskold, Mining 
Engineer. 

STEAM ON COMMON ROADS, fully 

illustrated. By C. F. Young, C.E. Cloth, 12s. 6d. 

THE ENGINEER’S POCKET REMEM¬ 
BRANCER, for Engineers, Architects, Surveyors, 
Builders, &c. An Epitome of Data, Rules and 
Formula;, applicable to Civil, Mechanical, Marine, 
Hydraulic, Lighthouse, Telegraphic, and Railway 
Engineering, Surveying, &c. By Francis Campin, 
C.E. Cloth, 5s. 6d. 


London: ATCHLEY & CO., 106, Great Russell-street, Bloomsbury. 







A NEW WORK ON 

MINING, ENGINEERING, LAND AND RAILWAY SURVEYING: 

By H. D. HOSKOLD, 

MINING ENGINEER AND SURVEYOR. 

Price 30s. clotb. 

This Work has been undertaken from a conviction that there exists no work on that subject, at least that I am 
acquainted with, which contains that practical, scientific, and reliable information which is best calculated to 
advance the Mining interest , and to aid those on whom devolves the direction and management of this branch of 
industry. With this view, I trust to show a new and reliable system of Mining Surveying, based on mathematical 
principles, by which the Miner’s Compass may be dispensed with, and the errors arising therefrom obviated, by the 
introduction of a New Instrument, by which Subterranean and Surface Surveys may be performed to any degree 
of exactness, and the one may be connected to the other without the aid of the Magnetic Needle; which New 
Instrument I have found to be capable of beautiful results, and will be found highly beneficial to all, and instructive 
to those unacquainted with the subject. 


Some of the Contents of the Work. 


The Miner’s Compass, and its errors. 

Practical Geometry. 

Practical Rightangled Plane Trigonometry. 

Nature and Use of Logarithms. 

Practical Oblique Angles. 

Plane Trigonometry. 

The Vernier Scale, as applied to Surveying Instru¬ 
ments. 

Subterraneous or Mining Surveying—Sec. 1. 
Description of the New Instrument. 

Adjustment of the New Instrument. 

Traversing Underground. 


Levelling Underground with Spirit-level, &c. 

Setting out Underground Curves. 

Land or Surface Surveying in connexion with Under¬ 
ground. 

Surveying Mineral Localities for Working Plans, &c. 

Setting out Railways to Mines. 

Longitudinal and Transverse Sections. 

A New Set of Tables of Distances, from Planes of Me¬ 
ridian and Latitude or Traverse Tables, calculated 
to every two minutes in the Quadrant, and by dif¬ 
ferences to twenty seconds, and for any length of 
Lines. 


The whole illustrated by numerous Plates and Engravings. 


REVIEWS. 

“With the extending introduction of underground railways at the main centres of population, the points of 
contact between civil engineering and mining engineering proper have very much increased, and thus a good work 
addressed to both classes of the profession ought to meet with a good reception. The book now before us appears 
to well fulfil the desiderata of civil and mining engineering. An introduction—excellent in its matter—is furnished 
to the book by Mr. Mark Fryar, ‘Lecturer in the Glasgow Mining School.’ The first chapter is on the miner’s 
compass and its errors, and it is one of the best in the work. The principal chapters, devoted to subterraneous or 
mining surveying are excellent. The adjustment of the theodolite—traversing underground—setting out railways 
to mines—longitudinal and transverse sections—are all handled by a man evidently thoroughly acquainted with 
these operations. Mr. Hoskold also publishes for the first time several ingenious devices and improved plans for 
surveying, such as a new plan of uniting surveys, that we strongly recommend to the notice of our readers. The 
traverse tables at the end of the book will be of very great use to surveyors. Without having practically tested 
Mr. Hoskold’s new form of theodolite, we like its appearance extremely, and we would recommend an intending 
purchaser of a theodolite to give his attention to this form of the instrument.”— The Civil Engineer and Architects 
Journal, December, 1863. 

“We must hail with satisfaction and pleasure all efforts which are made with a view to bring about any 
improvement in any of the departments of practical mining. It is our special province to bring before the mining 
public all the information which comes within our reach, and which has a direct or indirect bearing upon the 
practical science or commercial question of coal-mining. Combining, therefore, a great pleasure with an important 
duty, we would introduce to the notice of our readers one of the best books which has ever been published on 
the subjects of mineral surveying. Looking at the table of contents, we find the heads thereof such as will at once 
very favourably impress the mind of the mine-surveyor— e.g., ‘the miner’s compass,’ ‘practical geometry,’ ‘nature 
and use of logarithms, ’ ‘practical plane and oblique angled trigonometry,’ ‘the Vernier scale,’ ‘mining surveying,’ 
‘adjustments of the theodolite,’ ‘traversing underground,’ ‘surface surveying,’ ‘setting out mineral railways,’ 
‘longitudinal and transverse sections,’ ‘calculations of areas.’ Mr. Hoskold is the inventor of an improved theo¬ 
dolite, and his book contains two well-executed drawings, showing in a clear manner the principal parts of two 
different instruments : one is called ‘ Hoskold’s miner’s transit theodolite,’ and the other ‘ Hoskold’s miner’s transit 
theodolite, with supplementary telescope and plain sights.’ A useful coloured sheet is given at the end of the 
work, designated ‘Examples of modes of delineating different descriptions of land.’ Throughout the book there are 
illustrations of various methods of surveying under conditions of intricacy and difficulty, and practical problems 
are solved in a simple and intelligible style; and what we would point out as a special excellency is a most compre¬ 
hensive and invaluable set of ‘ tables of distances from planes of meridian and latitude, calculated to every two 
minutes in the quadrant, and by differences to twenty seconds.’ Concerning these tables, the author says, ‘ The 
proof sheets were carefully compared with the MS., corrected, and read over three separate times, by different 
persons each time. A new proof was then taken from the press, compared with a duplicate of the preceding ones, 
and afterwards every number composing the tables was recalculated. They were then returned to the press for 
alteration, and finally stereotyped.’ 

“We recommend Mr. Hoskold’s book to every mineral surveyor. No mining office should be without it, and 
no surveyor should be ignorant of the very accurate methods of surveying which it teaches.”— Colliery Guardian, 
Aug. 22, 1863. _ 


London: ATCHLEY & CO., 108, Great Russell-street, Bloomsbury. 







RAILWAY CONSTRUCTION. 

SECOND SERIES. 

By W. DAYIS HASKOLL, ENGINEER, 

LATE A RESIDENT ENGINEER ON THE SMYRNA AND AIDIN RAILWAY (ASIA MINOR); 

Author of “ Railway Construction” and “The Practice of Engineering Field Work.” 

In Two Vols., Imperial 8vo, Illustrated with 91 Folding Plates, with French and English Scales of subjects 
particularly useful to Engineers, Contractors, Students, &c. &c. Price 31. 3s. 

These Two Volumes, completing Mr. Haskoll’ s Work on “Railway Construction,” will be bound to 
correspond with the former Two Volumes ; the Four Volumes can be Subscribed for at Atohley and Co.’s, 
tor 51. 5s. 


CONTENTS. 


Differences in the conditions of Railways in Europe and 
in high thermometric and partially inhabited re¬ 
gions ; influence on elements of Construction, na¬ 
ture of Works and cost. Imported labour ; im¬ 
ported Materials—Lands— Privileges—Concessions 
—Contracts and Specifications—Deposit of types of 
construction. 

Camps and Labour Stations : their establishment—pre¬ 
sent and ulterior value—their buildings. Timber and 
sun-dried bricks—Description and management— 
Truck system and control—Labour Payment—Fever 
and sick seasons. 

Earthworks — Cuttings and Embankments—Cost—- 
Tools—European and native gaugers—Drainage and 
carrying off flood waters. 

Roads, Rivers, and Streams — Summer and Flood 
Waters—Examples of various cases and management 
—Torrents and Mountain Districts—Entire altera¬ 
tion of regimen—Treatment and special provision in 
Bridges and Culverts—Dimensions—Foundations— 
Inverts—Wing Walls—Bond—Masonry and Brick¬ 
work—Altering Stream Crossings from skew to 
square—Large spans for rivers—Small spans, sheet 
piling—Inverts, with buttress cut waters and deep 
foundations—Cost—Crossings for flood shallows— 
Archwork. 

Brick-making. 


Passenger Stations, Stores, Warehouses and Sheds, 
adaptation to native cultivation and industry— 
Masonry—Timber and treatment of Iron—Glass- 
Ventilation—Earthquakes — Minor stations—Tem¬ 
porary or permanent. 

Timber bridges and viaducts, permanent or temporary— 
their design and construction. 

Stone and brick bridges—their design and construction. 

Aqueducts and Culverts. 

Wrought Iron plate girders—their design and con¬ 
struction. 

Wrought Iron triangular girders—their design and 
construction. 

Wrought Iron lattice girders—their design and con¬ 
struction. 

Wrought and Cast Iron in Piers, Pillars, and Foun¬ 
dations. 

Wing walls and retaining walls in a scale of graduated 
heights, from the best French and English Examples 
—Dock and Dock gates. 

Timber Jetties—Timber and Wrought Iron Landing- 
Piers. 

Teredo navalis and creosoting. 

Cranes for various purposes of Timber and Wrought 
Iron. 

Wrought Iron and Timber fencing, gates, &c. 

Permanent way. 


REVIEWS. 

“We are always favourably impressed by a technical work well furnished with illustrations—a good print or 
drawing can be understood in all countries. The character of the volumes before us will thus be very fairly defined 
by an examination of the ninety-one well-executed plates forming the main portion of the works. We have thus 
some twenty-four plates of road bridges, bridges of masonry, timber, and iron plate, embodying most of the 
constructions required in ordinary practice, all of which have been practically carried out. Culverts of different 
sizes, ranging from six feet to twelve feet, are illustrated in about eight plates. Six plates fully describe different 
descriptions of stations of brick and stone, or of timber merely. Docks, dock-walls, locks, and entrance chambers ; 
sluices, and landing-piers, and the varied rolling stock and mechanical fixed plant of a railway, such as gates, level 
crossings, cattle-pens, cranes, permanent way, are all fully illustrated. The plates are well lithographed, their light 
and shade lines being almost as clean as those formed by the drawing-pen of a practical draughtsman. The titles of 
the plates are given both in French and in English. We believe that a French translation of the work has lately 
been published in Paris. The dimensions, however, are given in the English foot measure alone, but scales in both 
the measures are furnished to each lithograph. Although the work is nominally a second portion of Mr. Haskofl’s 
previous book on ‘ Railway Construction,’ it is in reality mainly devoted to the railway practice in the East, and 
more especially in the Levant. Mr. Haskoll is evidently an experienced and able civil engineer. The 
three first chapters are devoted to what may be termed, in the words of George Stephenson, ‘ the engineering 
of men’ in the East—everywhere, according to the same authority, the most difficult of all branches of 
engineering. We have a complete working specification and form of contract for a line of railway undertaken 
abroad. The last seven chapters treat on the engineering properly so-called—the engineering of matter 
—of the East. The nature of the works required to meet the peculiarly heavy rainfall of the East—the 
cuttings and permanent way—temporary and fixed stations—roads and tramways—plate, lattice, and trellis girder 
bridges—docks and jetties—are thoroughly examined from the point of view of their adaptations to the peculiar 
requirements of all high thermometric repairs. The book contains many excellent suggestions—such suggestions 
that could only proceed from an engineer practically acquainted with the novel conditions of Eastern railway 
practice.”— The Builder, Nov. 28, 1863. 


London: ATCHLEY & CO., 106,-Great Russell-street, Bloomsbury. 









31$ M f 

&T! 


ISTA ~I 
(>3 

NOW READY, IN TWO VOLUMES, 

Octavo size, containing 1100 pages of letter-•press, with full Illustrations. Price, Bound, £4. 


THE 


HANDBOOK OF SPECIFICATIONS 


OR, 


PRACTICAL GUIDE 


TO THE 

ARCHITECT, ENGINEER, SURVEYOR, AND BUILDER, 

IN DRAWING UP 

SpftiMiims aitir Contrary fur Writs an& tasfrarto. 

Illustrated by Presidents of Buildings actually executed by the following and other eminent 

Architects and Engineers :— 

ARCHITECTS. 

Y. Thomason 
J. P. Gandy 
W. Forrell & Son. 


G. F. Scott 

Sir C. Barry 

J. Dosbon 

R. Abraham 

Mons. Hittorff 

W. Tite, M.P. 

B. Ferrey 

S. Angell 

J. B. Bunning 

T. Hamilton 

T. H. Wyatt 

J. Shaw 

H. Baker 

T. Cundy 

G. Mair 


Robert Stephenson 
T. Page 


ENGINEERS (CIVIL). 

J. Simpson 
Lock & Errington 
&c. &c. &c. 


H. Mawley 
J. W. Brydone 


Preceded by a Preliminary Essay, and Skeletons of Specifications and Contracts, &c. &c., 

And Explained by numerous Lithograph Plates and Cuts. 

By PROFESSOR THOMAS L. DONALDSON, 

President op the Royal Institute op British Architects, 

Professor of Architecture and Construction, University College, London, M.I.B.A., Member of the various 

European Academies of the Fine Arts. 

ACCOMPANIED BY A REVIEW OF THE LAW OE CONTRACTS, 

AND OP THE RESPONSIBILITES OF ARCHITECTS, ENGINEERS, AND BUILDERS. 

By W. CUNNINGHAM GLEN, Barrister-at-Law, of the Middle Temple. 


REVIEW FROM “ THE BUILDER.” 

“ In these two volumes of 1100 pages (together), forty-four specifications of executed works are given, including 
the specifications for parts of the new Houses of Parliament, by Sir Charles Barry, and for the New Royal Exchange, 
by Mr. Tite, M.P. The latter, in particular, is a very complete and remarkable document. It embodies, to a great 
extent, as Mr. Donaldson mentions, ‘the bill of quantities with the description of the works,’ and occupies more 
than 100 printed pages. The contract specifications and correspondence connected with the erection of the Houses 
of Parliament occupy eighty-two pages, and are accompanied with a plan of the principal floor. Some of the 
tenders for the work here given include lists of prices. 

“Amongst the other known buildiugs, the specifications of which are given, are the Wiltshire Lunatic Asylum 
(Wyatt and Brandon); Tothill-fields Prison (R. Abraham); the City Prison, Holloway (Running); the High 
School, Edinburgh (Hamilton); Clothworkers Hall, London (Angell); Wellington College, Sandhurst (J. Shaw); 
houses in Grosvenor-square, and elsewhere; St. George’s Church, Doncaster (Scott); several works of smaller size 
by the author, including Messrs. Shaw’s warehouse, in Fetter-lane, a very successful elevation; the Newcastle- 
upon-Tyne railway station (J. Dobson); new Westminster Bridge (Page); the High level Bridge, Newcastle 
(R. Stephenson); various works on the Great Northern Railway (Brydone); and one French specification for 
houses in the Rue de Rivoli, Paris (MM. Armand, Hittorff, Pellechet, and Rohault de Fleury, architects). The 
last is a very elaborate composition, occupying seventy pages. The majority of the specifications have illustrations 
in the shape of elevations and plans. 

“We are most glad to have the present work. It is valuable as a record, and more valuable still as a book 
of precedents. 

‘ ‘ At the commencement Mr. Donaldson gives some suggestions on the Principles of drawing up a specification ; 
a skeleton specification for erecting a building ; hints for specification of dilapidations; a model contract; general 
conditions of contract for engineering work (drawn up by Mr. James Simpson); model forms of terms for letting 
building grounds. 

“About 140 pages of the second volume are appropriated to an exposition of the Law in relation to the legal 
liabilities of engineers, architects, contractors, and builders, by Mr. W. Cunningham Glen, barrister-at-law; intended 
rather for these persons than for the legal practitioner.”— Builder. 


London: ATCHLEY & CO,, 106, Great Russell-street* Bloomsbury. 















































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































